Well, you can do that thing you said, but I'm pretty sure someone must have put a video tutorial on youtube or something like that on how to raise the ground near a foundation. If you find something like that, you may be able to put 1 extra square in front of where the garage is, put a door, and then raise the ground near the 1 extra row, so that it looks like a ramp. You'd probably have to use the CFEF cheat, though.