I would be cautious about thicker windings or more turns. There is room to add, but this is a PM alternator with a PM voltage regulator. PM regulators work by sinking excess capacity to ground.
The voltage regulator on the f800 is that thing on the left side with all the fins to get rid of heat. It already gets hot enough to toast bread, increase the alternator capacity and your voltage regulator may melt down.
It is certainly possible to increase capacity of the charging system, but for safety sake, the voltage regulator and wiring between alternator and battery would need to be upgraded too.
Beyond any doubt though, you could greatly increase the robustness of the stator insulation, which would seem to be what is lacking on at least some of the stock stators.
P.S. I am told BMW intends to eventually start selling the stator alone rather then only the whole alternator. This at least should reduce the cost of the failing part.
Owned to date. Honda Aero 50, Honda Elite 80, Honda Elite 250x2, Suzuki Katana, Suzuki RF600, Yamaha YZF1000R, Kymco Xciting 500, Suzuki GS500, Suzuki Burgman 650, BMW F800GSx2, BMW S1000RR, Aprilia Scarabeo 200, Aprilia Caponord, Aprilia Sportcity 250
I love and miss you Jeneca and I'm sorry.