You are suggesting something EVEN stronger than me, while you call my version “reaaaallly OP”. I don’t play ToS, so I cannot comment on that. I’m going to disregard this “if people cheat, it’s really weak” argument.
Snoops are way less rare, since Noble is starting BD and Illusionist needs to be the third convert and it needs to be an unseen game. Regardless, Snoop is also as you said metagameable, however it is still powerful, because it can access at least the singular claim the recipient has at that moment. Mental Blur will have the same base usefulness, because it can be combined with Assassin.
Confirmability is a risk, but that does not mean that all evil abilities need to be unconfirmable. Bewilder on Invoker, shouldn’t be removed, just because it reveals an Invoker is present to a single person. Knowing it is an outing ability, the user should be smart about using it. Herbalist’s drug is the same way for example.
By the way, Possessor can also facelift as BD with empty logs to try and get the court to think there would be an Illusionist. Even though, I really don’t think it is as blatant as you are making it seem.