Reaper and Chicken have grown on me even though I hated them at first, but a Gen1 debut without them would have been much more orthodox and kept much more drama out of HoloEN, permanently changing HoloEN. I won't say for the better, but definitely it would be more Japanese and in-line with idol culture. We'd miss out on some good content, but also a lot of the more crass content that brings down the entire group, so I don't know if I would call that good or bad. I think without a Calli figure to take the heat off Gura, Gura would have quit since she was dealing with alcoholism and other issues during the first few months after departing from her Senzawa persona.
As for Gen 2, I have admittedly not watched them enough however for the most part they have all been "safe." Fauna concerned me since she's a massive slut IRL, but she's played it safe (fake, but safe) since her debut so I don't see her causing drama since she enjoys her income, which only leaves Kronii during her long-stream episodes (she gets migraines or something and becomes loopy? I don't know), and I haven't watched Kronii enough past her debut and collabs to form an opinion about that. Bae is a true otaku which comes across as a gap moe but we probably wouldn't get that side of her if Gen 1 had debuted the way you wanted so I don't know how to feel about that.
Overall I think HoloEN would be "boring" the way the newer HoloJPs are boring without the bad apples so I can't hate them too much. It took me a long time to come to that conclusion though. Kiara provides a business sense and pushes corporate boundaries in the background to allow for new/different content, and Calli, despite being a wigger, provides a different musical outlook and takes the heat off other member's antics by being twice as despicable as any of the others could ever hope to be. IRyS and Bae couldn't be so smug/gap moe degenerate as they are without Calli as a baseline to work off of. None of Gen2 are particularly great on their own, however they all work well in collabs both with one another but especially with Gen1. Mumei by herself is a bit of a control freak and bland (makes sense she's a college liberal arts student) when not in psychopath mode such as during the Needy Streamer playthrough, but she has good art symmetry/contrast with Ina, helps Ame actualize ideas, and makes for an excellent conversational partner with Gura since their total two braincells combined is like watching two bakas come together to create something new and exciting in their own baka way. Kronii's smug pairs nicely with most of Gen 2 and being good friends with Ina IRL lets the two of them crack jokes in a natural and expansive way. Sana is just a bundle of pure fun bringing Aussie shitposting to the table.