Unless you use aluminium fixing bolts (not a good idea
) you will still have galvanic corrosion issues. But isolating a stainless a frame from the hull is easy enough, just use nylon backing pads/washers between the two.
Bolting through the floor is the tricky bit, all depends on access to the underside of the deck etc. Corrosion still shouldn't be much of an issue above the waterline anyway if there is small points of contact between dissimilar metals if they're maintained properly, Tefgel is good stuff especially on threads.