Certainly there will be players who want that opportunity. I would say it's not something that has was ever included in previous BG games (and related such as IWD, NWN, etc.) and that is it is why it is so alien to me here (I'm a big fan of games like The Witcher, Mass Effect and enjoy playing those preconceived characters by the way). I think it's a little ambitious to try and cover both a satisfying single player experience and a fully fleshed out Origins character system. They might pull it off when it is finally released but like much with the game at present, it's a bit of a hybrid system and suffers for being so.
BG3 in a nutshell right there.
Especially apparent is the contrast between Origin Characters and Tav. Tav really needs: -an Origin system like DAO or -many more dialogues where you can personalize Tav. Companions ask you where you're from, what are your goals, etc. PoE did this iirc?
Alternatively/in addition, the Origin Characters should be extremely fleshed out in the world. If every OC has even a third of the special dialogue lines/personality/interactivity of the world that is given to Geralt/Shepard/etc, that would be amazing. It will be difficult to do that successfully for 5(+?) characters, but hey it could be done. Unfortunately we won't see the majority of their quests/interactions until Full Release.
Which always leaves me wondering why comparisons are made to full games, instead of a Chapter/Act in them, since that's essentially what we have now. Mass Effect, for example: We don't develop our full romantic relationship until we're on the way to Ilos. That's 90%+ of the game completed. Here it's roughly a third? This pattern repeats in ME 2 and 3, the full romance arc isn't completed until we're on our way for the final mission. So people are essentially comparing apples to oranges, but think it's apples to apples. We're not even close to that.