The idea of having Russia extend to the banks of the Dnepr is one option that seems to be on the table, but I am not sure that Odessa and the southwest wouldn't also be involved (and Hell, for that matter, there's no reason for Putin to not take Kiev if he wants it), because it would give Russia a direct border with Transdniestria and allow it all to be absorbed into Russia - I'm not sure Putin would want to leave Odessa out in that case. There is a new bill in the Duma that would provide for procedures for new oblasts to enter the Russian Federation. South Ossetia and Abkhazia might also choose the opportunity to end their nebulous unrecognized independent status and join the Russian Federation.

The interesting thing is that the blowback seems to be calming down as everyone realizes that there are no good options here. I actually wonder if the West didn't leak this phone call (see link below), supposedly intercepted by pro-Yanukovich Ukrainians, because delegitimizing the Ukrainian Maidan demonstrators would be a wonderful way to allow the West to turn its back on Ukraine and not suffer serious consequences. Essentially Paet, the Foreign Minister of Estonia, is very critical of the lack of public order in Kiev and also indirectly indicts the Svoboda Party of Tyagnibok and Right Sector of all the sniper shootings.