I think I'll leave the Bonisagus aside for now (I don't have a clear picture of what to do with him besides "investigating the rock"... and trying to integrate creation of essential traits into hermetic theory would break one of the greater limits... wouldn't it?).
So, for other ideas:
Cri (provisory name) is an English Criamon trying to fight his Wratfull personality trait. Cri came to know about Ireland first through the works of Gerald of Wales, and deciding to visit the country he learned that much of Gerald's works was biased by prejudice. He believes the English invasion is a consequence of misplaced anger of the englishmen, and that if he himself can control his anger (the cessation of strife within) while on Hibernia, than the conflicts in Hibernia will also subside (the cessation of strife without).
Cri is a pacifist (well, he is trying), and while he has no significant Mentem expertise as of now, it's possible that he will develop in that direction someday. At the moment he believes that using Mentem to control his anger is not proper. His current focus is Auram.
I'd think of giving him some ties with the church, nothing too big, but I'm not settled on that yet. May just end up him being friends with the monks on the north of the island.
Note: Stories for him would focus on non-violent conflict resolution, using Auram (and eventually other Forms) to protect allies and stop enemies, but generally aiming for diplomacy first.
Tyt (provisory name) is a Tytalus apprenticed in Circulus Rubber, descendant of one of the two Tytali who founded CR. His patter believes that Inchmore's resistence will fail unless there's a Tytalus involved... But Tyt couldn't care less, to be honest. This is just his patter trying to push an agenda on him. He is still going to help Inchmore, because he wants to piss off the English.
I'd think of gearing Tyt to be a master of intrigue and developing a network of agents to strangle the mundane resources of the English magi.
As for Arts, I'm toying with ideas. While Mentem would be useful for the master of an agency, I'd like him to be someone who grows into the role he decided to take, so he'd probably begin with a focus on something else. Tyt would eventually develop towards a more generalist approach, using magic to solve the problems that can't be dealt with easily in another way.
So, these are my two current ideas. Both seem fun to me, so I think the issue here is the opinion of the troupe in regards to what seems easier to manage/integrate.