Hey, kind of a random idea. As of now, the teambuilder itself is a tad disorganized, it's really just a long list of teams. This isn't so bad when you have 5 or 6 teams, but when you get to like 400 it's really hard to keep them all organized and such. I think it would be nice to have "boxes" were you could store teams for a certain format (or they could be customizable) so that is would be easier to keep track when you have a lot.
On another note, it might be nice to be able to customize the pick a tier screen. A lot of people don't like certain formats at the top left, and could save time by having their favorite tiers there. In addition, changing the name of the categories could be nice as well. Also, this could change the default tier from randbats to something else. Personally, I'd like to move some other metagames in place of NU and custom, and move randbats to a different place. I'm not saying this should be universal, but people should be able to change it around maybe.
I'm not sure how hard these are to implement, but I think they'd be pretty well received.