I had a few thoughts about AR. It's entirely possible other people have said these already but I wanted to get them out here nonetheless.
1. Make banning Medic prohibited. This obviously isn't a huge issue, but it will happen once in a while if you make AR into a league or even just a pug group or whatever. No medic makes the game way less enjoyable to watch imo, so it might make sense to just make sure no one bans it.
2. To follow up on what other people have said about weapon bans, why not have one primary, one secondary, and possibly one melee weapon ban per team (I'm worried banning gunslinger or GRU would make engy/heavy unviable)? So if engy and sniper are banned, then there will be six weapon bans in total, and they will all be on the seven remaining classes. That could encourage different class bans (which as ninjanick said is a problem), for example someone could ban short circuit which was the main reason engy got banned.
3. Something which many teams have done to great effect is to almost capture the point and then get off it until you need the cap. I would like to see the capture progress revert really quickly, to discourage that behavior. It seems like it would motivate more aggressive play and make it more difficult for one team to sac into another and then have the last player recap. I could definitely be wrong on this one, it's just an idea I had.
4. Other people have definitely said this, but a (3 second maybe?) delay on the minicrits while on point is really needed.
Thanks to all the people putting time and effort into this! Even if it doesn't grow into something big, it's really encouraging to see innovation coming from within comp TF2.