I think that just drawing minsc from a 20 year old game into a new game written by different people in different context means that he wouldn't be the same, unless the writers are super talented (and honestly I don't think Larian's writers are talented enough).
So if only bringing minsc is a very complicated writing work, creating him as an origin character is even more complicated.

Larian's Biggest Oversight, what to do about it, and My personal review of BG3 EA
"74.85% of you stood with the Tieflings, and 25.15% of you sided with Minthara. Good outweighs evil, it seems."