Give changelings different objectives

[ZeWaka]

Not sure how great this is, but you could have a 'Frame' objective.

Frame the Medical Director as a Changeling and have them killed by someone other than you.

You could also have minor specific but not specific 'Absorb' objectives.

Absorb a Head of Staff
Absorb a crewmember from the Medical Department
Absorb a crewmember while in the Medical Department