The self-defense forces of eastern Ukraine are more than capable of holding their own.
Urban combat is not what armies like to do. In Stalingrad, during World War II, the German army was ground up like sausage as the Russians gave no quarter and made them fight for every inch of the city. We all know the outcome.
If the Maidan regime is foolish enough to try it - its downfall is simply a matter of time.
A matter of a few weeks, at best.
They're done.
Russia is not going to put up with what's going on, even if they DID start it.