A few thoughts to that:
I went through hell re-fitting a 2021 Ribell (non RS) with factory grips afterwards. They connect to an ECU where also the illuminated „E“ - that one that lights up in configurable patterns during charging on top of the tank - connects to. Both are pin compatible but the harness insulation is all black. So, the dealer has to retract the insulation to actually identify the wire colors. My Ribelle had the carbon tank cover, so no illumination. The dealer was not aware, picked the wrong one, and BANG. This resulted in a four-weeks stay of my bike in Modena back in 2021 for troubleshooting and correction. So my strong advise if you decide to do this: Make your dealer aware!
Next, as posted the bikes VCU needs to be made aware of the heated grips.
Last not least, they really do not get too warm. Like probably a medium setting of aftermarket heated grips. Nowhere near like burning your fingers, what I have seen on highest settings with my BMW R1200GS or also with Daytona aftermarket grips.
Fitting aftermarket grips on a Ribelle/SS9/Evo, the 12V supply for the USB ports are fused 15A. Typical aftermarket grips draw 40-50W meaning they draw 50W/12V=4,1A, so there you have your power source as long as you do not use USB with heavy load in parallel.
The Experia as aux 12V supply separately fused with 15A.