Nemesis Draft, yes. That should be here. Poro King's removal, yes. Replace it with Snowdown Showdown because that mode is so much less unbalanced.
But BMB does not need to come back. It honestly wasn't that fun. Let's go over what it was.
It gave you the ability to make minions that your team almost never interacts with, but make it hellish for enemies to waveclear or try to come back. Plus it made 4v5s completely impossible, instead of the very difficult that we have today. Still salty about that one.
It made a bunch of OP new items that pretty much shafted ADCs and paid glorious tribute to mages and supports. Seriously, ADCs got one item that gave them a little bit of escape and a shitty spin-off of Runaan's Hurricane. You know that when the item that is one of the weakest of the bunch gets added to SR and becomes a massive balance problem for months, there's a problem.
And the last, and probably the worst, it feels the same as SR. If you don't look at the minions and play a fighter or AD assassin or marksman or sometimes even a tank, you're not going to notice anything different. Every other game mode makes the game feel different from SR. Ascension is very zone control-based with Xerath to spice it up a little. URF is super fast-paced, very noticeably so. Hexakill gives you an extra guy, which is a huge change. One For All gives everyone the same champion, which is, once again, very noticeable. BMB just didn't feel any more fun and created more problems than things it was good for.