Arena needs a commander block list for Brawl
The single biggest problem with brawl on arena is the tendency to play against a relatively small pool of commanders, with certain commanders in particular tending to show up again and again and again. There's apparently some sort of opaque matchmaking system designed to create "fair" commander match-ups (so high-tier commanders tend to get paired against other high-tier commanders, etc.), but this actually just makes the variety problem worse.
Sure, maybe I don't get paired up against Kinnan much if I'm running a janky commander, but I'll still end up fighting whatever the most popular low or mid-tier commander is constantly. And hey, maybe I don't actually mind playing against Kinnan ( I mean... I DO mind, but that's a separate issue), in which case you're reducing my pool of opposing commanders for no reason.
The obvious solution is to just let each player decide for themselves which commanders they are and are not willing to play against. This is how it works in casual tabletop settings, and it's de facto the way it works on arena too, albeit with more wasted time, since whenever I get paired against a commander I hate, I simply concede immediately rather than play a match that will just infuriate me.
It would be much more efficient and ultimately make for a much more diverse play experience if I could just tell the matchmaking algorithm ahead of time which commanders not to match me against. This would also eliminate the problem of broken commanders like Omnath rendering the format unplayable until they get banned. Honestly, you could even unban Omnath - no skin off my nose, so long as I'm not forced to play against it. And if someone's choice of commander is resulting in long queue times because lots of people have it blocked, you could have a message pop up telling them so, and thus encourage people to try something different.
(All of this goes double for historic brawl, of course, where the ratio of available commanders to commanders that actually see play is even worse.)