Some thoughts on the College of Collaboration.
It is true that there is a less focused body of knowledge/expertise than there would be for the RSRR charter. However, that doesn't mean there isn't one. The body of knowledge here is a broader one, one of various types of magic users and/or priests, particularly focusing on the people you expect to be working with. A pooled body of knowledge. College wizards getting a better understanding of how their other-wind colleages do their thing. The main problem here is that the varying factions here have a lot of secrets they're not willing to share, which makes the pool of shared knowledge smaller, but the secrets are hardly all-encompassing. I do think there's still a fairly sizeable amount of knowledge that can be shared.
This doesn't have to mean your understanding of your own Wind has to suffer, rather, I think that in some ways understanding other disciplines can help further your own. I feel like my understanding of game design helps me be a better writer and have a better grasp of people and the systems they live in, for example. Or, an example from Avatar The Last Airbender: Uncle Iroh, a firebender, developed his lightning redirection.
Also, in general, there's no reason you have to stop studying your own Wind to work here. Much to the contrary, the more understanding you have of your own Wind, the more you can contribute.
Finally, all that aside, a very key skill that this Branch College would revolve around, a shared topic of expertise, is... well, collaboration. The thing about interdisciplinary collaboration such as this is that it requires a certain kind of open-mindedness, ability to respect people with dramatically different perspectives than you, and general good etiquette. Also, learning how to explain your viewpoints to people with little understanding of your field.
This mindset is actually a pretty damn difficult one to find, so creating a branch college that attracts people of that mindset and cultivates that mindset certainly has merit, I think.