We live in a bilevel. It is a modular home placed on a poured concrete foundation with 8' walls. You walk into our home and either go up or down 8 steps. We added onto our home 1,200 sq. ft. Much of the original home is unused and wasted space. E.g. Original kitchen and living room was upstairs. We moved them downstairs. I want to gut original 24'x36' house and lower the floor, creating a crawl space and main area with 12' ceilings. Stairs would be moved to back of house to access addition. Basically turning home into trilevel, us living on main floor, addition is bedrooms for company. Husband said it would be cheaper and easier to move. But our location, on the lake, is perfect.

Anything is possible, at least for the most part, with enough $$$. Husband raises a good point. In one of the houses my son owned, we raised the sunken LR by 6 1/4". 2X6 and 3/4 T&G Advantex flooring on top of the slab. Had to reset an exterior door. HOWEVER, how high are you thinking?

Could you draw the 3 elevations for us?
12' ceilings may look very strange in a small house, especially if it isn't all one big living/dining/kitchen. And that's more than gutting, because the windows will now be 4' too high.
Also, many towns with lakes have extremely strict zoning laws, and get stricter every year.
And.... you really want a crawl space? I can't stand them. Dead mice, you name it, and I won't go down there.

Aw, couldn't you plan this before the construction? We had really well contractor (Retail Construction - InsideSquad Inc.) who really cared about wishes of the owners, restructuring is few times harder. I can only wish you good luck.