That’s a good start, but it wouldn’t deter against Observers visit tracking/Princesses. I personally put in a lot of work for FoL Merc and had reasons to go that route, so of course I’m going to tout them here. Do with it what you want.
Your targets can be converted and are likely to get converted, because one, they have a Merc and are more likely to live longer and two, if you get deduced, they are great conversion targets, because evil will also get a Mercenary on their side. Knowing this, it will also be beneficial to be wary about openclaiming Mercenaries and their targets, because it will make BD more suspicious about the targets being converted. This is kind of the mechanic in FoL that prevents a Merc openclaim to a degree.
So far they don’t know the class, so an evil doesn’t need to out to whoever claims to be their Mercenary (which can also be faked by Mystic private matters, I actually remember this being done a lot back in the day).
I’m always a big fan of confirmability at a cost. That’s why FoL Merc, can prove themselves beyond reasonable doubt with… taking the lynch. This “you would be pardoned” could be a great mechanic for evil “Mercenaries” or Mercenaries with evil targets to get mislynches on others, but now it can’t be, because Mercenary targets are informed they have a Mercenary through confirmable private matters links, so you now always have 3 players claiming the same thing, which is nigh impossible to fake for evils, so extremely confirmable through that day ability. Having it also be confirmable in that way negates the former to try and get a mislynch through it, because “targets” will never agree to the Mercenary being real. I would think about if it is necessary for the Mercenary and their targets to work together so explicitly and having them be able to confirm themselves to them.
The FoL version here is that the Mercenary sacrifices themselves to be the lynch, which would negate this dynamic and be helpful for both scum/town/the Mercenary itself. It’s confirmability at a cost, which is the missed lynch on an actual scum, but now a Mercenary for the town and the cost for the Mercenary is well death, so they can’t protect their targets anymore.
There is a similar story with Butler Party or Physician self heal or the confirmability of a Noble/Mystic helping the target throughout the day. Or also starting Assassin/Cults being worse targets than a Mastermind that cannot be checked and is naturally death immune. There is no way to win here, so best is to just allow it all and just have it be natural difficulty variance for the Mercenary. Things like Merc to Prince, I would definitely not allow either though.