Yeah, what I foresee happening would be more “Merc tries to avoid claiming or fakeclaims in the early game, reveals they’re actually a merc later on once it no longer seems like BD can afford to randomly lynch neutrals.”
Consider this, say. Someone claims knight or something early on. They whisper someone D1 or D2. Then, several nights into the game, without being prompted, they say “actually, I’m XYZ’s merc.”
I think most BD would at least consider accepting it (an evil would be unlikely to risk changing their claim when not under pressure.) I’ve seen Alchemists do similar things, and while they can prove by healing, it tends to get accepted even if they haven’t. Especially if eg. the NK is dead and the merc has helped vote up Cult / Unseen.
If they change claims on the stand they’re probably dead. But there’s a point near the mid-late game where neutrals can generally out themselves safely if they do it when BD is becoming desperate. And, of course, this would also give evils a window to lie.
Basically, what I’m saying is that the mercenary would actually have to work to earn the BD’s trust - vote up other evils, try to help find the NK, come up with reasons why it can’t be you, and try to convince the BD that your target is also BD. You wouldn’t be able to publcly claim Mercenary D2, but you wouldn’t have to. You want to be able to set things up so you can claim Mercenary D4 or D5 when everyone’s roles start coming up.