The best thing about a BG3 would have been BG with a different ruleset.
I mean, sure, 2nd edition is way better than 4th (and whatever 5th will be, I guess), but it really pales in comparison to 3.5.
For the following rant I am assuming rules as seen in the BG series, and how well they serve a PC game (I won't make too many assumptions about PnP):
I'm not kidding. BG series are great games, but they would be vastly superior if they used 3.5.
Character progression in 2nd edition is just totally fucked up. Why do classes take a different amount of experience? That's just completely arbitrary, and a nice source of unbalanced nonsense.
If every class advances at the same XP, all is well, and 3rd edition shows that. This also balances out the classes, as now all of them feel equally powerful.
Generally progression in BG is too slow. When you start a character in BG, it can take 2-3 hours until you actually level up. That is simply not acceptable. If I wouldn't have been like 14 years old when I started playing it, I would never have found the time to play the games. Now don't get me started with ADD or something like that, I have put hundreds of our into BG and still do from time to time. But that painfully slow progression just sucks.
Another thing is, and here I think it really is the fault of the ruleset, that progression doesn't really feel like you get much stronger. With warriors, rangers, etc. you get more HP and can attack better. That's it. What a boring reward! With mages, bards and the like, you at least get some spells, at least
something to show that you can do more than before. In 3.5, any class is interesting to level up, as you get more spells, more feats, talents, etc. There's something new and interesting coming with almost every level. Playing a Fighter in BG is the most boring thing ever, and although I put hundreds of hours into that game, I never played more than some hours with a Fighter. It's just soooo boring.
Also, combat is far more interesting in 3.5 than it is in 2nd edition. Just imagine BG was turn-based (I know you can do it!) and compare it to KotC. Who wins, huh?
In BG, playing any Fighter-style character is nothing more than "Go there, hit". That is all a Fighter can do. And as if that wasn't worse enough already, your party just needs such a meat shield (at least in early levels). Again, in 3.5 any class can do multiple things that are at least mildly interesting. Also, you're not outright dead if you do not have a meat shield.
Which gets me to another weak point of 2nd edition in BG. Early level combat is ridiculous. If you are not a Fighter, everything will kill you. Everything. I think I was even killed by those Candlekeep assassins multiple times. That's a tutorial fight. It should NOT do that....
Okay, early levels are also a pain in 3rd edition, but it's not
that horrible.
So.. you know, instead of BG3, how about porting BG series to 3.5?