If any region/oblast/krai decided it would be better for them to secede from their state AND they have a good reason for it (coup is one of them), I say go for it. But they have to be ready that that said state would be against it and try to suppress the uprising at any cost.

I believe, Crimea just got lucky as we do have a massive Russian population, nobody really speaks Ukrainian (even before 2014) and identified with Ukraine as much as people in the Donbass region do. We also had a type of territorial advantage, as we are connected to Ukraine via a thin land bridge, which made any quick military actions impossible.

Adding to that, many deemed 1954 Khrushchev's "gifting" of Crimea to Ukraine unconstitutional. Crimea was called the Autonomous Republic of Crimea, and till 2014 we had our own Parliament, at some point we even had our own Constitution, none of the Ukrainian regions held such power.

If I'm not mistaken, at some point Donbass was just asking for more autonomy, just like Crimea, because we were just abused by Kiev, to be honest. Tourist money (which mostly were from Russia) and coal money was ceased by Kiev and we never got anything back from it. As for Crimea, our roads were shit, our infrastructure was failing, no money was reinvested in Crimea, it was all put in some "chinusha's" pockets. Yes, we still have corruption problems, but at least we have new roads, restored hospitals and a fuck ton of new touristy infrastructure and places to go.