Another point is that removing Putin probably won't do anything to change the desire to expand Russian influence.

The Siloviki, the people that rule Russia, agree with Putin's analysis that NATO is a threat and Ukraine is an artificial country created to be a bridgehead into Russia's strategic heartland. Which is an opinion which predominates among the Russian general public.

Remove Putin and you'll likely get someone with the exact same worldview. Perhap someone more hawkish, such as Patrushev, or more militarily capable, such as Shoigu.