(L, I know your working on pits, sooo...)
I think the best way to implement pits would be to make a combo type a mix of Tile-Warp, and Damage, with an addition that plays falling animation. Thus, one could have a pit that deals 1/2 heart daage, and warps back to the entrance of the room al la bottemless, or one that deals no damage and warps to a different screen, like the between floors fall. Two birds, one stone.