The problem is Baldur's Gate isn't designed with mods in mind. I knw there are a few very good efforts (Darkest Day?) but generally making a NwN mod would be easier, as after all NwN was designed exactly so people could make there own mods and be a 'Dungeon Master'.
But I agree BG is a better engine, I just think it would be difficult
I agree the one of the worst differences between BG1 and BG2 was the removal of all the inbetween town areas. I used to like exploring the pathways and going off course to the coastline etc. In BG2 you only really got to visit a place if it had a major quest, until later in the game when the small forests appear.