I'm not a fan of the permanent party, since I can't really see a reason in favor of it.
Eh, it depends what they do with it. In D:OS2 post-mortem Sven said that companions in D:OS2 were sort of added at the very last minute. They might have reasons for killing off companions which they never got to explore in D:OS2.
I tend to stick to one party in RPGs anyway - sure I will switch them to do companion quests, but I feel I don’t really get to know them unless they will spend majority in time in the party. In that regard I preferred BG1&2 approach where there wasn’t any “party camp”. People where in your party or they weren’t.
On the other hand,I always found Obsidian’s party conflict like at the end of NWN1 or PoE2 interested concept that never got really explored. If companions just get killed that would be lame - but if they end up staying in the story “maybe some will take Rafael on his offer, or become Absolute minions” things - this could be interesting.
So my question would be not what locking party removes from the player, but what it adds. If, like in D:OS2, all it does is remove companion quests - then it’s rather pointless.