This. Just selecting a target charges the meter, but if nobody targets that person with a kill, the doctor doesn't get outed.
Ideally, the doctor wants to save people, but the moment someone is saved, mafia will learn who did that, so combos where a power role claims and get protected forever are not encouraged. At the same time, if mafia fails to kill the doctor fast, they get a prize for surviving, so it's a high risk, high reward mechanic.
That said, I haven't even started writing the other 8 roles yet, so when I'm done I'll compare them to see if any are much stronger or weaker to each other, which may prompt me to go back and tweak the doctor. This is just a sample so you guys know how the roles will (probably) look like.