So you have collisions. ("Does Y mean "yank"? Or does it now mean "to"? Well "to" can't be T anymore, because that's now the motion up command.")
So you have to either remap everything back to qwerty positions, and learn the new mnemonics, or keep the letter associations the same, and give up on the clustered motion commands.
I'm thinking it's probably better to do the latter, but I'd love to hear from vimmers that use non-qwerty layouts.