I like Bridge as is. It is powerful, yes, but it is not trivial to match it up. I feel like having that kind of super-combo is neat, and the feeling you get when you pull off KC-Kc-Bridge-Bridge-Bridge is awesome enough to keep.
I think NV-Bridge might outrace KC-Bridge. Also, Possession might make you think twice about trying for the KC-Bridge megaturn.
I don't think Coppersmith should be nerfed. It's already a weak card; stacking with KC is pretty much the only way it ever sees real use. And even with the stacking, it usually isn't dominant because you ALSO need +Buy and a way to draw enough Copper to make it worthwhile.
For Adventurer, maybe search for 3 treasures and keep 2 (so you have a slightly better chance of getting good treasures with it).
For Scout, make it part Victory type so it can draw itself. And maybe make it worth 1VP.