Guilds need odd jobs, kinda like the bounty things in BoarderLands. Walk up to a board, take a piece of paper with a quest on it, go do said odd job, get signature from person who wanted job done, and then turn paper into to guild to get paid.
Then as you build up a rep in the guild, they may ask you to do a special job...one that ties to that guilds main quest.
Then based on your rep in the guild, you get a nice promotion. With that comes harder odd jobs, but better pay.
Not to mention have other guild members do more than just stand there. Have people coming in and out, make it look like you're not the only one in the guild doing something.
And no stat skill checks. If they want us to have a 25 in destruction, don't just have the computer look to see if the pc has that skill high enough. Give the pc a spell that requires the pc to have a 25 of destruction and have them use it for one thing or another before the rank up. And besides, once you're in a guild, they shouldn't care how you get the jobs done. Sure, when you join they should probably care, but once you're in as long as you're useful and bringing home the gold the guild would not care, exept for the highest ranks.
I agree that it shouldn't have stat checks, but still be mage oriented. Like if you want to complete it as a warrior you can, but it will be a hell of a lot harder and you may need to go find/bnuy scrolls for some things.
Nice idea with the jobs. I think that a good way to do it would be to have a "join the mages guild" quest that is difficult rather than just talking to someone. Then, you should have to complete a few "randomised" jobs, and then raise your rank to getting specialised jobs from the guild leaders, and keep going a bit like that until you get into whatever prestigious place they may have in Skyrim (if any).