Almost zero good outcomes in the What Ifs column except the unlikely chance that Russia negotiates rather than starting a new campaign with a new strategy.
i however suspect putin will not enter any negotiating phase from a place of weakness, and losing a quarter of your bombers thousands of miles into your territory is about the weakest point they've been at for the entire war. perhaps the initial push to Kiev which was perhaps not even in earnest being stopped was it, but i think its now. even asking North Koreans to send troops wasnt the weakness the media perceived it as. North Korea got to rid some hungry mouths and regained the world stage, likely paid in oil or coal for soldiers.
i think its most likely they either take off the gloves in earnest, or send in a missile campaign that is truly terrifying, so they can at least start negotiations from a neutral position.
Honestly I'm still in the "nothing ever happens" camp, the null hypothesis is often the safest. The weight seems to be on the side of Russia not overreacting.
Ukraine would only take these actions if they wanted to bait a Russian reaction. Russia just committed to a 6000 body swap during the peace negotiation. They're winning the war on the ground and clearly planning a new summer offensive
These are reasons for Russia to either not react at all, or more likely, make token retribution that doesn't actually upset the status quo, like when Putin fired off an Oreshnik. He could fire off more Oreshniks, if they aren't nuclear tipped it won't change anything.
Does Russia have the ability to just launch enough conventional missiles and drones to raze the civilian infrastructure and housing of Kiev to rubble right now? They probably do. Is it likely? I still don't expect it