Could you maintain hand flying skills by simulator sessions alone? Is the simulator of today accurate enough? What are the shortfalls of the FFS? Apart from the obvious one that a FFS is not an aircraft!
Believe me but if you do not have the skills to hand fly a fidelity compliant flight simulator then you sure are going to have a real problem flying the real thing. Regulators around the world accept that fidelity compliant simulators can be used for type ratings, instrument ratings, recurrent training. if a pilot is having trouble flying an ILS in a crosswind in a simulator then he will almost certainly run into the same trouble in the real thing.
So the answer to your question of could you maintain hand flying skills by simulator sessions alone, the answer is definitely yes. IMHO