I'm hoping we get a very diverse cast of companions.
Ideally, we get companions so diverse that you cannot recruit them all. Due to them not agreeing with each other (Such as Evil/Good characters, or companions with particular prejudices against certain races)
I don't wish for "Bring all companions for large battles" because my experience of that is it's more tedium than anything actually cool (To say nothing about how balancing around people bringing everyone will mean that if you dislike any companions it sucks because you have to bring them along or it'd make combat much harder - Unless we get a super OP Lone Wolf feat and forgo almost all companions entirely...)
If we do get to recruit more companions than are able to fit in our party, I hope they are handled better. Not just killing them off instantly like in DOS2 or having them sit in camp forever like in BG3. I'd want to see them have some autonomy, meaning that if they're not in the active party, they'll actually be out in the world trying to further their own goals, meaning you can stumble across them and help them out with their personal quests without having to bring them in your party (With also the potential for consequences for ignoring them, such as them making poor decisions, being injured or even killed because they went alone and you didn't aid them).
Heck, maybe if you'd recruited enough companions and they got along well enough, they'd roam the world as another party and would be more successful at achieving their own goals.
Which also brings about another aspect of companions - Intercompanion relationships. Having them interact with other companions and gain/lose favour as a result. Meaning certain companions can develop rivalries if they don't align with each other, or can develop strong friendships (Or even relationships) if they get along well.
I know the game Lost Eidolons: Veil of the Witch had intercompanion relationships, whereby bringing along companions would allow them to gain positive relationships from certain events which lead to special intercompanion dialogues and bonuses when fighting together (In the form of stat boosts when stood next to each other and chances to proc helpful effects like auto casting a heal when the ally is attacked, or retaliating against a monster that attacks them). This was neat even if only one sided due to only having positive gain, even for the companions that hated each other.