The house was built probably in the mid to late 20's. Has wood lathe and plaster. Old BX for wiring. The wire is "okay" not really brittle, but the covering is extremely fragile. Scares me..

I would like to replace it. What is entailed in pulling new. What would you use? Romex or AC ? Some access to a very small attic. But not overhead access to all areas.

I'm not against cutting a few access holes, but I'm not ready to completely gut the interior.

Your opinions are appreciated.

This requires a good knowledge of basic framing, and any unique to the local standards and age of your home.

Also will need knowledge of how to operate a fish tape. Using gravity whenever possible with a nylon string and a weight helps a great deal.

There are available up to 6 foot long very flexible drill bits for old work.

You need to imagine a path that crosses the least amount of wood framing for each cable. Planning each path helps with combining runs when possible.

There are a lot of little tricks, or techniques, that help, but on a case by case basis. Difficult to explain here, for me anyway.

If there is limited access from above, how about from below? I prefer romex/nm cable. If you are trying to add receptacles I would come from the top or bottom and push a wire up/down the wall to the hole that you have cut for the receptacle box. Lath and plaster walls are usually not very well insulated and generally are pretty easy to fish wires through. That is unless your house has the dreaded fire stop blocks in the stud spaces, then you have to get creative. I have come across walls that were impossible to run wires through. In that case you can always use surface mount wiremould. Be sure to use the correct gauge wire for the amperage of the circuit you are running.
Good luck!