However, irritatingly, alpha doesn't work because Construct doesn't seem to like the way Paint.Net saves alpha. I had to remove the black stuff manually. Ugh, what a pain. Don't use Paint.Net for alpha in PNGs, folks.
Edit: Or GIMP either, apparently. God dammit. How the hell do you get proper alpha right off the bat with these things?
Now, the next main problem to make this viable is Z-Order. In other words, layers. Oh, yeah, and collision, I forgot. You either want some things to collide, or some things to not collide, basically...
... Then again, for collision, you could just have a second tileset for collision stuff. That works well. Z-Order is still a problem, though.
Edit: Also, you want to be able to work with multiple tile sets at once, and by consequence, multiple sprites. So, basically...