I know we have the champions but I'm missing a detialed fighters guild quest line. So I had an idea for possible DLC.
You get a note staying the fighters guild would to open a chapter in skyrim and would like you build it up. From there you get a number of quests that allow you to slowly build a guild hall (customisable based on how you complete quests) and a membership and evently become the leader, this could maybe bring you into conflict with the champions and lead to some quests where you have to fight them. One quest I thought of was: you hear a rumor of a great unarmed fighter living near riften and you set out to sign him up to your new guild but you'll gain his trust first.
What do think?