By basically working as a limited but functional beta software, Fusion does not have a foundation or complexity that exists in SW.
So, to answer your question, I think it would be more difficult to go from Fusion to SW than the other way around. It is copying Solidworks flow while trying to add Rhino surface modeling by buying tsplines (tsplines had been a plug-in for Rhino before Autodesk bought them) and a lot of it's modeling UI from Evolve.
Well, Fusion is sort of headless as far as a direction and methodology.
