Battle Plus v2 is not just an improvement, but an evolution of v1 battle in all respects. I don't see any reason to play the default Battle Mode when Plus adds so many things that makes battle so much more enjoyable and pleasant. The improvements on top of v1.1 that allows to create custom gamemodes for BP will also greatly increase its replayability as soon as programmers get to sink their teeth in the codebase.
However, I will say that although all of the custom modes are very fun, polished and thought-out (seriously, there's some good ideas here!), I feel there are some flaws that prevent me from truly enjoying them.
There's various (hell) gamemodes that don't have a time limit (Randomizer, Item Rain, Emerald Thief, to name a few). I don't see why the former two shouldn't, since they're Bumper Battles with an extra mechanic added on top. Emerald Thief should have a timer as a failsafe - I've been involved in so many chaotic fights in Emerald Thief that have gone for longer than +5 minutes just because whoever holds the emerald in a big netgame will not hold it for long. A 5-minute time limit would help here.
Chaos Ring Runners is strange, because the rules don't feel evident even if you get a gist of what it is about. People with the least rings get eliminated, but sometimes you're not too sure if you have enough if there's too many players by checking the miniranking.
Curiously, you did add the ! exclamation bubble on top of players who have none, so my thought is that it was the indicator of if you have enough rings. Cue my confusion when I die with one chaos ring.
There's also no reward for Karma SPBing people. Normally this is the incentive for players to keep playing even after dying, but I've seen people either AFK or do nothing or just doing it out of spite. This mechanic should be retrofitted back - I don't see why players shouldn't be able to come back into this gamemode.
Hooligan Roundup is excellent - my favourite gamemode. The only real problem I've seen is that jails don't split as often as they should, so I will often see cops camping (which is incredibly favourable for the cops due to their extra range), and sometimes the players' jailed position, depending on the level, may have them fall into death. Also, players who get freed might get immediately chomped, which is not exactly fun. I've seen someone suggest that players should naturally respawn into the level instead to prevent these issues and I'm inclined to agree to it being a proper fix.
Ring Runners is something I find fun because of the alternative win method. However Ring Debt sucks so much, and makes it really difficult to come back into a positive number if you keep getting hit. I know the game makes it a little easier on you if you're in debt, but it doesn't feel enough. But overall I do think this is a great gamemode.
Egg-fection has a similar problem Virus (another gamemode on the MB) had - it's hard to tell who's infected at a glance. I recommend setting the players' sprites to fullbright, colorize them, and do as much as you can to make this evident. However, I have to praise you for the decision to make item hits also count as infections, it helps a lot with the pace of this gamemode.
I'm also going to say it: Ringslingers absolutely rocks. Please make this a regular rotation gamemode.
All in all, congratulations on the v2 release! This was a lot of fun to try out on release and it was definitely one of the most exciting releases in the MB for a while. Please keep up the good work.