I don't really care if 4 or 6, but if it stays 4 and I can create a custom party I've already a group in mind with no rogue, cleric or wizard. Not the most optimized party, but I'm confident it will work.
Expecting lvl 12 as cap and subclasses from the player handbook:
Vengance Paladin (maybe multiclassed with Warlock for roleplaying)
Dual wielding Hunter Ranger with urban terrain for thief tools (multiclassed to Battlemaster)
Lore Bard
Wolf Totem Barbarian / Moon Druid
Everbody has a sprinkle of healing, bard as support and a it of magic since I don't like mages anyhow and the other 3 should have no trouble to stand on their own two feet. Would I recommand this party to others? Nope, but nothing that I've seen so far in BG3 makes me think that I would need to play a classic tank, utility rogue, wizard and cleric group. I've played with such a group (because of available NPCs) through EA and they never felt really needed. I noticed even beyond the added stupid DOS2-gameplay you can play how ever you like in combat and it works.
If the party size gets increased it will probably just mean I will give the companions a shot, but at this point BG3 could be the first game with NPCs were I won't even bother with them. Not ment as a disrepect to the writing team, but I'm a bit annoyed by them and all this DOS2 companions approach. I simply am not interested in the DM's player characters.
