honestly I like your suggestions but it seems to go against larian's design here, they're already hinting at the fact you probably have to drop companions until you reach a total of 4 max, it's what they did for DIV OS2 as well tho honestly having played it with a mod that removes that limit and having played through the game I really don't see why exactly narratively it was required when with a mod the game keeps on chugging A O K aside from 1 encounter where your old companions suddenly come up again as ghosts. It didn't add anything fighting 2 guys that fell of the boat into the underworld who I honestly have had 0 connection with cause they've missed out on 2 arcs worth of story and development.
Larian if you're reading this, your previous implementation of excluding party members from the total group in DIV OS2 added nothing narratively, it just locked players out of content that required replays and it felt like a really cheap method of getting replay value when I could've just experienced the whole story (as I did with the mod) in 1 playthrough, please don't repeat that in BG3, instead you can interweave it with the gameplay and have the player character have to balance the wishes of the party and approval ratings to keep the party whole and not falling apart and at each others throats considering shadow heart and lae'zel seem to hate each other on racial bias alone, I see a great amount of potential for char development towards either a lovely rivalry or perhaps a reconciliation as the 2 party up with the main character and through adventuring together start to tolerate each other.
Another note: character development should include the companions of the MC as well as the MC and not only the MC, as it stands now approval ratings only apply to the MC when honestly it seems that their approval of your other party members seems just as important, however there is a problem with ALIGNMENTS and this is something that's a big point of contention and debate amongst DMs as to what interpretation of alignment is best suited for what campaign with some DMs applying purely rules as written with many other DMs having homebrew rulings on alignment and its related mechanics as to allow more freedom of expression rather than forcing an evil rogue char to be a constant asshole the whole party.
