My apologies for coming to this a bit late, but you know... family and stuff at this time of year. (Actually, some drumming too, including in the open air which was a first for me.)
Having looked at Jeff's reasons for dismissing some great suggestions but that I thought my problematical as I thought about them, I'm wondering if you're going to find a term that exists. I think you may have to make something up.
My initial thought was P.A. but I don't think that captures it. I'm a bit cross with myself that I didn't write down my second thought immediately as it's gone now and I thought it a good one. <sigh> Maybe it will come back.
Monitor?
And someone must have said 'counsellor'?
So, after that I was getting into made up things:
I can understand how you might not want to use fragta (not overly attractive in itself although I don't know the source material), but how about a nod to it by using Jao as the word? Or perhaps Jow?
What about something like 'Bounder'? Someone who sets boundaries - or tests boundaries with the noble.
Also, I quite liked the idea of say using 'jeeves' - but in the 57th century no one knows why - i.e. completely detaching it from its servant connotations to just be the abstract noun (as Imperials would think it). Of course, the snag with this is detaching it from those connotations in *players* minds. But in which case you could corrupt it to 'jeef', 'jeev', 'jefs' (long 'e') or even 'jeff' ;-) or something and maybe play on the supposed (but incorrect) connection with 'jefe' (although I believe that's pronounced rather differently).
Then getting more random/abstract - an 'eric' - again no one knows any etymology for this.
conte
contex - which my dictionary gives as 'weave together' which sounds rather ideal for your purposes
and while I'm on the Cs, how about a coryphaeus - elegant, sounds learned and although it's dictionary meaning isn't quite what you're after, a) no one in the 57th century is going to know that and b) I'd be surprised if many in the 21st century knew its origin either!
But don't forget language will have shifted in all those centuries, so take something that's nearly right and corrupt it.
Or is this the moment for a lovely word I found a while back - kumihimo - 'gathered threads' - the idea being that the person in question draws different strands of the noble's learning together - physical, weapons, mental, social etc and weaves them into the polished young sophont required...
Of course, as you've been my jeff these last years with regard to some of my Traveller writing, I'd go with that term... :-)