In the context of 'sudden collapse of Russia' in general? Probably just make sure back channels to whoever has control/custody of Russia's nukes are available.

In the context of 'sudden collapse of Russia' in general? Probably just make sure back channels to whoever has control/custody of Russia's nukes are available. The west's primary goal should be ensuring the safety, security, and non-use of Russia's nuclear (and whatever WMD) arsenal in the event of collapse. Beyond that, I don't think there's a lot the west can actually do? Attaching western support to any one would probably completely de-legitimize them as an immediate post collapse player.