I mean what Russia needs is a deep change of regime and mentality.

Frankly, I doubt that reducing the country to ashes or close, would do that, on the contrary: the more a population feels threatened and vulnerable, the more it gathers around it and refuses to accept change.

A much smarter move would be on the contrary to be specifically kind to russians, why not by offering them asylum, papers, food, etc. Show them that their government is the problem, and that they have no reason to want war.

If they have military dominance, start forcing open passages within russian territory, protecting anyone who wants to escape. And obviously, be genuine about it, and do try to actually give them a proper life, don't start packing them in refugee camps and telling them to shut up.

That would weaken much more the russian government, make it much easier to trigger a regime change, and whoever escaped and wants to go back to Russia can, once the situation improves.

Feels much better than to just push Putin to force-recruit all civilians and send them to their deaths, with the ones not fighting starving to death instead.