I can imagine playing the vanilla game quite a few times actually. I mean, it's going to be impossible to do all of it in one playthrough, and no matter how many times I play a game, I always find something that I missed, whether it's a dialog choice difference, or who I killed/didn't kill. Just from the gameplay video I last watched, I can see something that could come out different based on "leave the wounded" or "tend to the wounded". That's just one thing, in one encounter. So I don't see mods as being all that important.
I played NWNs for 5 years, but if you think I was in the OC/expansions, you're wrong. But that game was built entirely to show what you could do with the toolset, and I went nuts after I got bored just running around the internet seeing what others were doing. By the time I moved on, I had started my own module, and had added scripts, story and other content to two other modules, including a piece of music for one. That was, however, the selling point to the game in the first place. The tools for Origins were hard for me to wrap my head around, but frankly, that's because I'm far from a professional at that kind of thing, and it was, in all fairness, a professional grade toolset. I wish I still had the screencaps of the areas I'd built in the NWN2 set. However, I didn't get Dragon Age for tools, even though I did look at them. I got it for the story and the game, and I'm not heavily invested in mods for it. I do have the party camp chest, and 2 other mods, a respec mod, and the trailer edition, I think. So really, despite still playing the game, it's not because all the mods I got made it replayable. In fact, the only mod I can think of off hand that would make it even more replayable would be adding voice acting to the Warden's dialog, because after ME and DA ][, it just feels dry to stand there staring at people while they talk at me.