I can start, if you like.
In my opinion, there are six possible courses of action Russia could take. I will list the scenarios for you and quickly assess their likelihood.
The first scenario is Russia does nothing, and it was all a bluff. I believe that this scenario is unlikely because Vladimir Putin has set the bar very high in subjecting NATO member states to very specific recommendations. In addition, so far he has refused to compromise—on the contrary, he seems to be ramping up his demands. In other words, I feel he can't back down without losing face.
The second scenario is a limited intervention in the Donbass. Russia may want to do what it did with Georgia and spur on secession movements, eventually recognizing the independence of Lugansk and Donetsk. I believe that this is highly likely, because Russia has done it before. It doesn't cost Russia very much, other than exposing it to additional sanctions. The international community would be reluctant to step in and liberate the two areas. That would fall on Ukraine's shoulders.
The third scenario is a variation on the last one. It would involve expanding the current secessionist regions. The two areas do not occupy all of their provinces as defined in Ukraine's administrative structure. Russia could therefore help them gain control over more land than what they currently occupy. In my opinion, [Technical difficulty] this scenario is somewhat likely.
The fourth scenario is a limited intervention in southern and eastern Ukraine. In this case, Moscow would seek to establish territorial continuity between secessionist regions in the Donbass and Crimea. This would establish territorial continuity for Russia across southern Ukraine. I feel this scenario is somewhat likely to happen.
The fifth scenario is an intervention into half of Ukraine, all of eastern Ukraine, to expand military occupation to the Dnieper River, which acts as a dividing line in Ukraine. All of eastern Ukraine would be under Russian military occupation. This is somewhat likely, because Russia has mobilized the military capacity it needs to do it, so technically it would be able to pull it off.
The sixth scenario is an intervention with the intent to take over all of Ukraine. In my opinion, it's unlikely this will come to be, but I wouldn't totally rule it out.
Finally, the last possible scenario would be a general intervention against NATO. In my opinion, that's out of the question, because Russia doesn't want to start a third world war.