That depends on the character of the newly emerged Putinist Russia. I think, they said goodbye to rational economic behavior long time ago and instead prefer territorial expansion at any cost. If Russia had been driven by this consideration they would have continued covert support to the insurgents and encouraged independent DNR/LNR. Instead they removed the charismatic rebel leaders such as Girkin and allowed the rebels to be nearly destroyed, before they intervened. That is classic Soviet maneuver: use local proletarian base to justify a military invasion, then get rid of leaders with independent streak and gain direct control. In a place like Angola the sovs had no alternative to setting up a satellite state, but since East Ukraine is contiguous, I think they decided on direct annexation.
The Russians want compliant leaders. Annexation is always an option depending on how the West reacts. Moscow does not want the rebels to have an option of not being allied with Russia. And as you pointed out, they will destroy or allow the Ukies to destroy for them any one who shows the slightest sign of independence.
Ukraine could wind up split into three states.
1. The part that goes to Russia.
2. “East” Ukraine with Kiev as the capital, and not aligned with EU/NATO
3. “West” Ukraine with Lviv as the capital, as part of EU/NATO.