Sadly, I suspect it’s not that easy Pete.
The Russians have been pretty incompetent so far, but if they concentrate forces in the east they're likely to have better chance due to a number of factors.
More troops in once concentrated area is the simplest factor, but they'll also be able to make defensive positions and keep assets shielded in/near their territory.
There'll be some grave concerns about western weapons being used anywhere near the Russian border, so that caveat may impact on negotiations.
Regardless of what they may have spouted, Russia wanted the entire country; they've failed to that extent, yet I can't see them giving up the Donbas.
It'll be incredibly difficult for the Ukrainians to drive concentrated forces out of their land without exponsing their northern, NW flanks to a potential attack.