before I post this suggestion, three disclamers; (1) I did do a search globably and specific to the Ability forumns for this and found nothing. (B) Even though I did search, I suspect that this is one of those ideas thats been (pardon the pun) shot all the he11 somewhat in the same vein as the Swords ability tree. (3) I am without a doubt the worst searcher ever. 
So the idea; Has there ever been a discussion concerning making shotguns there own ability tree free from the rifleman ability? The thought I had was to make the tree branch off into special attacks that impement the different types of shotguns (12 gauge, 32 gauge, etc) and different types of shot used (buckshot, slug, etc). For example, your level 30 upgradeable could be a 12 gauge expert (obviously the actual weapon wouldn't be needed to be implemented, just the upgraded abilities. At twenty two you might have Buckshot special attack which could render the target blind or offbalance and 25 could be steelball which could be a situational speical attack where if the target is staggered using it could do damage. 27 could be slug shot and 30 being the title upgrade. Obviously this could continue for another tree (31-50). Anyway, if this has been discussed could someone forward me a link (who is better then I at searching...lol) I would love to find out what others think about this.
Look forward to hearing from every 