I wouldn't recommend hydros either. Look for some air bags.
If your dead set on switches, what you want your car to do will determine how many batteries, pumps, etc. you'll need. You can get away with as little as two batteries on up.
I hate to say this, but i had switches on my old Cutlass. 8 batteries, 10 switches, 4 pumps, and plenty of moves. Very fun to play with, but i'll never do it again.
