We already know blocks can
move due to gravity, and the Piston Mod takes it a bit further. What I think we haven't seen is a large collection of blocks moving in tandem, which is what would be needed to make it work. You are probably right that there are technical reasons why this wouldn't work well. The game never has a lot of blocks moving at once, and in fact if you quickly destroy a lot of blocks (such as with TNT) game performance drops dramatically. Given the number of constant chunk updates that would be required, it is probably not feasible. Ah well.