Just a suggestion that might be relatively 'simple' to do but that could extend high-level play a lot and make 3 imposter games with 10 viable:
Add an option for 'Blind Imposters' where imposters are not informed who other imposter(s) are, and are then also able to kill other imposters.
This means imposters will also have some guesswork to do in order to avoid killing their teammates, and crew members can no longer assume that slain players were crew members.