Are you sure? I think Larian just said you can fully respec companions. Link below, and the pertinent part pasted.
https://store.steampowered.com/news/app/1086940/view/3655285307835439472"In Baldur’s Gate 3, you have the freedom to respec not only your chosen protagonist’s class but also that of your playable companions and pre-authored Origin characters, whether you’re looking to make a few adjustments to their existing build, you’ve got a burning desire to experiment with entirely new playstyles and class combinations, or you just want to create an all-badger supergroup. Keep in mind that certain Origin stories are closely intertwined with their characters' respective classes. If you’re opting for a non-cleric Shadowheart or a Wyll without his warlock pact, this will undoubtedly influence your roleplay options in dialogues and the overall narrative for these characters. But their stories will instead be yours to create."