Yeah, my thinking is that it makes sense to have membership required to get the Fighters Guild, Mages Guild, Imperial legion and imperial cult to join your tower because those are imperial interests and Telvanii have historically been hostile to imperials. Uvirith's grave is way out in the boonies and it's going to be hard for the imperials to protect whatever assets they have there, so they'll want proof that you're going to welcome them before they move there. I'm not 100% sure about the mages guild though because the way BUUG implements it the mages guild person who comes to join you is kind of a "renegade" member of the mages guild seeking to avoid punishment....so it probably helps that the Archmagister isn't a member.
The thieves guild (or some criminal element) is going to spring up in any big city realistically, so I was thinking about just having them naturally appear and then if you decide they annoy you you can ask your guards to wipe them out. I thought about implementing a choice between the thieves guild or camonna tong, but camonna tong hate outlanders so much that they'd either not want to be in your town or would just not care what the Archmagister thinks.
Morag Tong is happy to have a presence wherever they're allowed, and there are even some writ quests that take you not to far away from there, so while they'll want permission I don't think they're going to require membership to be invited there. Plus, from a house wars perspective, it's advantageous to have a base in the Archmagister's new city.
The Temple I'm not sure about. Technically all the Houses are susposed to respect the temple, and even Sadrith Mora pays lip service to the temple. Vos has a temple too. At the same time the temple is struggling financially because of the blight and isn't going to want to waste resources without proof that they'll be treated with respect. On the other hand, UG might be an attractive place for pilgrim's to rest, the temple might be eager to keep an eye on the new Telvanni Archmagister, and while the Archmagister might not be a devout member many of the other residents might be. I think what I'm going to do is make it so that you at least have to complete the pilgramage of the 7 graces, and that after that the temple will be happy to build a place in UG.
Other things I'm thinking about adding (assuming it's ok with the author) are:
--Slave market (if you decide to approve of using slaves in your mine). I would probably put it near the silt strider platform.
--More Town Guards or amununculi
--Barracks for additional town guards or workshop for amununculi (Hlendresa's house isn't really large enough to be a workshop
The "other things" are all still tentative. I have the modding competence to adjust when the people come to ask you if you want them to build in your city and to do dialogue, but anything beyond small tweaks I'd have to find time to train myself to do
.