My wife and I recently purchased a 1950's home. The electrical meter is on the western front of the home (40' x 30') with a panel below it, another panel inside the house, behind the meter inside a closet, and a third panel inside a half-bathroom inside the attached garage (34' x 30') -- it's a StabLok panel which the building inspector said was a hazard.
I have done wiring previously; residential, barns, and stables; years ago, however I have an illustrated copy of the 2002 NEC and a handbook of the 2008 NEC, both of which I've gone over. I know that there are many code violations in the house and garage, hence I am going to replace much of the electrical installation.
The house portion will be "renovated" in a few years (i.e. demolished in plain speak, but "renovated" according to the local CA building permit codes) and a second (possibly third story) added. The garage portion (34'x30') will remain, however we will sheetrock the exposed studs and ceiling to protect the apartment above the garage (fire wall).
There will be a triangular-in-cross-section attic crawlspace (4' high, 10' wide) above the garage (next to the apartment under the sloping roof) which has enough room to run plumbing and electrical now; and add electrical cables in the future without having to remove sheetrock (we'll put an access panel in the garage ceiling when we sheetrock the ceiling).

I plan to install a new meter box with 200A disconnect on the south outside wall of the garage 53 feet from the existing meter, then the utility company will move the meter -- the existing meter location will be demolished in a few years. I plan to install a disconnect outside next to the meter box for a possible future photovoltaic installation (I'll do it now so PG&E won't have to return if we install PV at a future date; I'll also install conduit from the switch to the garage and to the roof to pull wires to the solar panels if/when required).
I may decide in the future to also install an automation system during the house renovation (Vantage by Legrand, C-plus by Square-D, etc.) where the light switches are CAT-5 wired and the luminaires (and other items such as A/C, heating, security) are automated by a central controller.
I note that the house has a kitchen and the garage apartment also has a kitchenette, so there are few extra circuits for a 5000 sq ft structure (estimated total structure area after renovation).

I will remove all three existing panels (especially the StabLok) right now, however I see that I am faced with three choices:
(1) place a 200A load center inside the garage behind the meter (with a disconnect so that I don't have to run outside {in the rain} when working on the panel)
Pros: a single panel will be convenient.
Cons: the branch circuit runs for the house will be longer, there will be a maximum of 42 breaker slots (yes double slots for oven, electric stove, dryer, two hot water heater will take up 10 slots, however 4 will be freed up when the two water heaters are replaced with one gas heater)

(2) place a 200A load center inside the garage on the wall nearest the house-to-be-renovated
Pros: the branch circuit runs for the house will be shorter, the panel will be nearer the boiler, water circulation pumps, etc. on the house side of the garage
Cons: the service disconnect-to-panel feeder will have to be about 40' longer in total, also the 42 breaker limit, panel location will be a bit tricky to work around a stairwell, exit door, existing water heater, existing laundry room, etc.

(3) place a load center inside the garage behind the meter and later place a sub-panel inside the renovated house
Pros: the branch circuit runs for the house will be shorter, there will be more breaker slots available in the garage, especially if I ever want to put in a drill press (I'm assuming that a small lathe or Bridgeport mill will require some funky 3-phase installation)
Cons:? what would be a good location for a sub-panel in the home -- I'm used to "utilities" being in the garage or basement

I know how to wire these three choices in accordance with the NEC, but which one would be best?
With all my prior wiring experience I never had a choice as where to place the panel, so I'm a bit stymied as to optimizing this situation. Cost is a secondary factor to quality -- we plan to retire in this home in a few decades, so I will spend what it takes for quality and convenience for my future maintenance work. I'll use all Square-D because it's what I grew up with.

Thanks for any suggestions!

Since this is a rather complex installation, is there a reason to distribute power like a commercial installation? Some things to consider:

1. A distribution center consisting of a few breakers (2-4) feeding multiple sub-panels
2. The sub-panels primarily located near the largest concentrations of circuits. One being the garage.
3. A lighting only panel(s) with home runs to each fixture. This would make it easier to add central lighting control in the future.

If you posted a floor plan using "go advanced" we might have a better idea of the layout.

Canadian Code says the main panel has to be inside the house within 5' of where the conduit from the meter base enters the house. i.e. if you cannot reach the other side of the garage by running a conduit outside the house, then you're stuck. Perhaps (someone correct me if I am wrong) you could have just a single 200A breaker on one side of the garage within 5' of the meter base, and then run to the main panel on the other side of the garage?

Our house is like yours, except worse. It is 95' wide with the service on one side of it (which also happens to be the garage, like your hosue). I put a 100A sub panel in the middle of the house in a closet near the kitchen. By code, the stove, second oven, and dryer still need to be supplied directly from the main panel. However, all the receptables, d/w, microwave, fridge etc can go to the sub panel. There ended up being about 18 circuits on that panel. Basically the heaters, subpanel, major appliances, and a couple of local lighting/ plug 15A circuits were the only circuits on the main panel. Everything else was on the sub panel.

I don't think I saved any money, but it sure was easier.

Are you really sure that the main panel has to be within 5' of the meter base. It would make more sense if they required a disconnect within 5' of the meter base. That seems to be happening these days in the US, but I don't know if it's code or not. These disconnects are located outside.

This is our code... perhaps yours is different. I don't have the actually code book to give you the words.

My 'electrical code simplified' book (an excellent book on Canadian code written by a former inspector) says the panel must be within 5' of where the conduit from the meter base enters the home. If you want to have a panel farther away than that, then you run the conduit outside the house. It does not make any mention of a disconnect in place of a panel, which is why I asked someone to correct me if I was wrong. It makes sense to me that a disconnect would be OK... but sometimes the code and common sense are not the same. I would not do it without checking with my local inspector.

In any event the US and Canada use different codes so I usually try and put a disclaimer in my posts to make sure that people know I may be following a different rule book.

Yep. It's always up to the AHJ (Authority Having Jurisdiction) and in some cases it's the power company.

Aha, I made a few errors.
By "CA" I meant California.
I know that the California amendments to the NEC do not require a service disconnect on the exterior at the meter, however I spoke with PG&E and they prefer a disconnect at the meter. Also I know that several cities and counties require a service disconnect at the meter.
Pros: the fire department can disconnect the power when there's a fire, I can disconnect the power when working outside and there is a problem
Cons: vandals can shut off the power without gaining access to the home (crystal meth addicts broke into and burglarized our rental where we live down the street from this home, so vandals are on our minds)

I've decided that it's probably better to put a 200A service disconnect on the exterior at the meter. I would also put a (unnecessary) 200A disconnect at the load center for my own convenience. I do not know of any requirements in the NEC, Caifornia code, or local code which requires the main panel to be within a fixed distance of the meter and the disconnect at the meter. Given KeepItSimpleStupid's comments regarding over-complicating the installation and rtw_travel's about a panel near the middle I would lean towards a single panel on the stairwell side of the garage: if I run out of circuit slots I can always add a sub-panel next to a load center there.

Will it be easiest to install a conduit across the garage ceiling and pull 2/0 conductors through it?
Or find armored cable with three 2/0 conductors and a smaller ground conductor?
I have never looked for 2/0 NM: although I will put a disconnect in the meter box which will make the conductor from the meter box to the load center a "feeder" (NEC definition) I might guess that there is little call for 2/0 NM and I'll only find 2/0 SE, which might be the simplest.
Although code permits 2/0 for service entrance conductors for a residential dwelling, given that I am going to add another 30 feet plus I am tempted to step up to 3/0, however I see that 60' of 2/0 conductor at 100A only produces a 1.2 V voltage drop, which is only 1%.

Most of the future equipment (boiler, water circulation pumps, air handler, etc.) will be located under/near the stairwell in the garage.

A rough house plan is attached.