I agree that a "donate" button should always be allowed.
However, I think being allowed (both through media like the Steam Workshop and renowned sites like Nexus) to actually charge for mods will quickly encourage a very unhealthy and ultimately deserted mod community.
Maybe this might work for some types of games, but having been pretty involved in the Dragon Age and Elder Scrolls modding community since Morrowind, I can't imagine this having a positive impact - especially considering the similarities I've seen between Bethesda's and Larian's editors.
Then again, I of course can't exactly predict how Original Sin's mod community will turn out.
Still, I might donate (and have in the past), but I certainly won't pay for something I believe should be an unofficial passion product; maybe for a small handful of modders the huge expenses of their work might warrant a price tag, but then we're talking about a completely different bag of beans.
No, I'm thinking about the tons of mods I've tried in certain other games, that promised all kinds of stuff but... well, let's just say my standard and theirs weren't exactly compatible. This includes enough information about the mods beforehand for me to enthusiastically give it a go. Of course I did appreciate all the work they put into it, but if I had actually payed for it I guess I would've felt kinda silly.
After a few times more of likewise experiences, I wouldn't have tried as much anymore, and eventually might have lost interest in the community altogether.
I realize that's just me, but I reckon there's a reason most mod communities of most such games either do not allow charging, or it simply doesn't happen because it's considered bad form.
