As the oenogists insist about protecting this kind of wine with heavy quantites of sulphites, I believe that "mutage" (adjonction of pure alcohol on the wine, to stop fermentation)
can prevent from using sulphites: this is a very old technique for conservation (some texts fom the 13th century mention it).
Minimum "mutage": 6% alcohol, instead of 10%
Late "mutage", in order to keep less sugar: the product remains sweet(50g/l sugar) but not too much (most fotified wine are 100g/l sugar)
"Mutage sur grain": the alcohol is added during the maceration of the skin. After mutage, the maceration goes on for another 2 months.