Logically, Ranis really just wanted to prevent Telvanni influence from spreading. Llarar is far from Telvannis, and seems to be establishing the beginnings of a base. If he is sided to the Mages Guild, I doubt he would get along with Ranis. Remember Ranis told you to kill him if he wouldn't join, so he isn't an old friend or anything. I'd imagine that he'd be much closer to you than to Ranis.

I'm not sure how well Masalinie would fit the Steward role, as she is only an Apprentice in the guild, so wizard is a very large jump. I think she would be a fitting gossip considering her trade, though how she would acquire any part of Ranis' history is beyond me. Llathyno Hlaalu seems to rather old, and probably knew Ranis' parents whereas Masalinie is of a different race, and is certainly not on the friendliest terms with Ranis (to the point of swapping detailed childhood memories). Then again, Trebonius knows. So perhaps it's common knowledge.

I'm not sure how to handle Llarar yet either. I think that his being Telvanni means he definitely needs to be included in Pax Telvanni somehow. I have a method to my madness on Masalinie as the new Steward. First, she's level 12, the highest other than Ranis in Balmora. The only Journeyman in the guild is Galbedir who is only level 7. I was thinking that if Masalinie can be built up as a gossip then it isn't too far of a stretch to make her know that rumor line about Ranis. Like you said if Trebonius knows the info is out there.

From the view of the Archmigister, Llarar would be a traitor.. at least if the archmigister had not convinced him to do so. This seems to bring into question the entire situation of a Telvanni, and the leader of it no less, being in the mages guild to begin with. I almost feel something of a rewrite is needed on most, if not all, guild quests when the Player is Telvanni, but that may be more trouble than it's worth. I can reason out that IF Ranis were expelled from the Mages Guild, so would Llarar. And I highly doubt the stuck up Telvanni would tolerate a traitor such as he. This would leave Llarar in an exceptionally unlikeable position, with no allies anywhere and a base right between 2 warring houses. I can imagine some anger toward the Archmigister if he didn't help return him to one faction or the other.

It's interesting you pointed out character levels, as Ranis is actually second in level, she is only level 10 while Masalinie is indeed 12 and all their stats reflect such. This makes me wonder what Bethesda was thinking, perhaps an allowance for a fight with the unlikeable Ranis as well as the prevention of killing or protection of a fast travel NPC. I'm not sure how far that goes as grounds for the change, it would need some... unusual coincidences at least.

I'm not so quick to dismiss Llarar as a traitor. If you were running Mages Guild quests either you convinced him or killed him. So, he could be one of the first NPCs we institute as both Mages Guild and Telvanni. Maybe make Llarar the new Steward in Balmora? Rather than look at Llarar as a traitor he may be one of the building blocks in tying the two factions together. That's my initial thought, anyway.

Then we would need to add a small snipit to Llarar and the Journal indicating he has NOT broken his ties with the Great House, as it seems to insinuate. I'm not against him being tied into both, just that it appears otherwise.

Hmm... I'm going to think on this. If possible I'd like to do this in a similiar way as RoHT. It'd be ideal if we can start Pax Telvanni after the PC finishes Mages Guild and Telvanni quests without disturbing the vanilla content. If not then you're right.

if that is somewhat settled, I think the next thing you mentioned was Ranis's revenge... assuming you actually removed her. I suppose if you wanted to work completely after the player is leader of both factions you could give the player another chance to remove Ranis, simply by the decree of an archmage (which conveniently you are). You could then reinstate Tiram, and still give Ranis a motive for revenge, though I find it illogical that she wouldn't try to kill you on sight should you join after becoming Archmigister of Telvanni.

I don't think it's really possible for the Player to side with Ranis, in light of her background. But I suppose a few of the Telvanni could be angered, or at least disappointed. most really wouldn't care.

Honestly, I'd like this potential mod a whole lot more if it was made for a player character who opted out of the whole Archmagister thing and is now a happy Master/Mistress.
It would increase the politial intrigue tenfold if you actually had to make short-term alliances and curry favours with your fellow magelords before you can get anything done.

the problem would be with trying to get past the current archmagister, as he is incredibly well known for being anti-imperial (aka anti guilds) and extremely suspicious of most anything that moves. I doubt any amount of politics would get him to make any change.

This sounds like a great idea. While my last Telvanni character was the exact type that would do the vengeful thing like RoHT has you do, I like the idea of a merciful, kind Telvanni master.