Russia has neither desire nor capacity to hold ukranian speaking regions.

Why would Putin or his sucessor willingly sign up for a neverending domestic terrorism problem for nothing in return?

Even if you believe that the ideological motivation is false, and the invasion is purely for resources, all of the valuable minerals are in regions that already speak RU and have invited the little green men to assist.

Arable land is something RU has a LOT of. Why would they sign up for a permanent counterinsurgency program for a <2% gain in farmland which will require extensive de-mining before it can be used for anything productive?