The left picture is my favorite part of the first ending: Nozomi appearing in the doorway gleefully and Eli right behind her, stiff and embarrassed. Given that, as well as the gap Eli leaves between herself and Honoka in the right picture (the only gap in the whole line of them), I like to think that this ending takes place in those couple weeks after Nozomi and Eli join and before the concert.
I understand why the anime skipped over those weeks, but it’s one of the most disappointing things the anime does, in my opinion. We see Eli go from antagonist to best friend in the span of 30 seconds, when the actual process wouldn’t have been anything like that. Eli’s stubborn. At this point she knows she’s in the wrong, that she has to be nicer to Honoka and the rest of the girls, but she’s too awkward to do it naturally. She’s going to keep being stubborn simply because that’s all she knows how to do it, and it’s going to cause friction in the group until she can calm down. There’s going to be arguments, disagreements over leadership (who’s in charge? Honoka, as the person who started muse? Nico, as club president? Eli, who’s been in charge of everything her whole life?), and while in the end it will bring the group closer, you could have an interesting story where they almost fall apart.
The one saving grace, aside from Nozomi’s magic, is that most of the group can’t hold a grudge. Nico and Maki are the only ones who stay angry (and Eli should be really glad the subunits didn’t exist because bibi meetings would have been awful), but eventually Maki decides she doesn’t care enough. Nico is good at staying silent and angry for a long time, but once she’s alone she gives in too, and it’s only then that Eli can start to relax and truly bond with the group.
This post didn’t quite end up where I expected it to go but basically: those two weeks after Eli joined would be full of character development and awkward bonding moments and I really wish we had seen them.