Of course this game will have NUDE mods at least one.
Same thing with SKYRIM. Skyrim game does not have nude without MODS.
However if BG3 is going to be for NUDE BABES that is up to Larian developers like example Witcher 3. I would not be my money on that BG3 is going to have full nudity in campaign like Witcher 3, but it will have violcence and perhaps Horror effects for 18+ age.
That said MODS are community freedom. If you do not want the nude mode then simply do not install it.
Saying things like back in the day BG1 and BG2 did not have nudity is pointless. Because back in the days when BG1 and BG2 was released there did not exist any mods.
I do no need this game so Larian enforce full nudity in campaign like Witcher 3, but that said at least nude mods than you from community example nude mods as in Skyrim! Well and no this is not some childrens game this is not going for some teens age rating!
I also like Horror and brutal action in movies and games and absolutely do not want this game going for low age rating.
What your young teen will play anyway? That is up to parents to be guards.
Offtopic about parents guard:
Personally I think bigger problem is that some young teen try hard drugs example Meth. Well and of course "every" teen never try alcohol before 18 age lol. That try booze is not so bad necessary, but hard drugs can ruin your life easily.