I proposed this idea in the Oblivion mods section years ago, and some showed interest to work on it, but nothing (that I know of) has come of it.
...and maybe this only works for a centralized location, like the Arcane University.

The guild could have each school of magic represented with its own master within that school. Quests that rely on that particular type of magic would be given, and you can raise in the ranks, and be given the appropriate titles.

It would be nice to have the opportunity to specialize within the other guilds as well.
So for role playing, it adds a nice game mechanic, as oppossed to just pretending.
Advancing within a specialization does not neccessarily cut you off from pursuing others.

Thoughts?

The Fighters Guild could have specializations for one hand and two hand... and maybe archery.

Thats a good topic I like the idea of having multiple sections within a guild you could focus on

Dark Brotherhood.. I think it would be nice if there were like 3 different sections. One for murdering/ Assassinations.. One for Going out, Helping and recruiting more people and another for Sneak attacks, and the stuff i left out lol.

Is that what you meant??