I think it's a pretty neat idea. I would think about how you could integrate with Bandcamp, as the bands you'll attract are a huge part of their band user base: bands whose fan base is small enough that a group pooling their money could influence the tour route, but who are rabid enough about supporting the band that they'll actually try to organize something.

I'm not totally sure how you handle the venue choice, but a crowdsourced database of venues to play at could be useful. If I'm acting as the booking agent, get me to add venue details (capacity, age restrictions, photos, contact info) to a public directory that other users could tap for their own booking. Maybe get small venue owners or booking agents to add/claim/curate their own entries.

This is kinda random, but I also think it would be a cool and unique gesture if the organizer could be given a way to arrange to "feed the band." This is just a very band-centric touch based on the fact that a touring band is always gonna be happy to be given a meal, but if the organizer had a checkbox that, for a fixed additional overhead cost, they could arrange to have a meal delivered, I suspect both bands and fans would think that was awesome. Even if it's just a big pile of big burritos.