When you advance through the ranks some of the missions or 'extras' could become interesting by you training other people...
Warriors guild;
Recruit five people to join the warriors guild, and train them to become recruits.
You could do this by walking around asking them, for instance your speechcraft would be needed for this in a way unless you specifically find orcs or nords for warriors guild. Or you could persuade them with gold or doing something for them.
It would be interesting to train up your own people rather than spend all your time being trained by randomers around the world.
For the mages guild it could be teach them how to weave a fireball and you show them a demonstration and shoot it at a target.
Thieves you could teach them a thing or two about stealth and security. Showing them the ropes of hiding in the shadows and lead them by example.
even if the final test for each one was to take them on the mission with you and bring back either all of them alive or as many as possible leaving you to train new ones seeing as the one or two stragglers died. You could set up the equipment for them, offer them potions etc.