Not had that much experience with a Fazer engine, but a dragging clutch causing difficulty in selecting neutral is usually clutch plate related if you have already discounted all the obvious stuff like return springs etc. If it was a hydraulic clutch I would suspect air in the system. But the Gen 1 is cable.
The clutch doesn't have to be dragging much to make it difficult to select neutral, have you tried running the bike with the clutch in with it off the ground, just to make absolutely sure?