He doesn't have to expose himself directly, any occupant or even local in russia's puppet government will be a prime suspect to get removed permanently, as symbolic and also practical gesture. He will still need to travel, meet people etc. and no hiding in bunker will be allowed for such a person, that's only reserved for putin.

There is already vicious spiral of oppression and resistance happening on those parts of Ukraine. He could be +-safe with protection on level of US president, but he won't have that. There are only few situations worse than to be considered occupant or traitor in place like current Ukraine.