I think it would be interesting if Ukraine forces somehow staged a counterattack, broke through the Russian lines, and headed northeast, right to Moscow. I know there is extremely little chance of that happening but it's just a momentary fancy of mine along with visions of Putin being hung for war crimes.
It's not as bad an idea as the futility of their current efforts. 469 miles is just a hop, skip and a jump these days. Send 50 teams along 50 different deer paths through the woods and you know at least a few teams would make it all the way.
I don't know what the personality of the Ukrainian people is like, but if they're revenge-oriented, I could see more than a few of them stashing away some goodies right now (perhaps even some goodies supplied by us/friends of ours or at least enemies of Russia/Putin), waiting a few years until Russia focuses somewhere else, and turning chunks of Moscow into rubble.
Probably a few Afghanis who wouldn't mind helping in that mission, probably a few former Soviet satellite countries, probably others, too. Putin / Russia doesn't have a long list of friends.