Please, change the party mechanic by having them not grouped together as default. Plenty of times a plan has gone to sh*t because I forgot to unchain the characters and they stumbled after me, when I already had them in position.
I don't understand. This sounds like a player problem, not a game problem. The feature is there and ready to be used. The issue is you forgot.
That is almost certainly something that will stop happening with more time playing.