If you have no other electric clothing I would start with electric jacket liner
type with heated collar forearms and kidney area
Surprising how warm the rest of you feels if the kidney area is heated - all your blood gets warmed
So given the limited output of the /6 I would put the first available watts into a jacket liner
Wear mittens loose enough that you can easily move your fingers about in them and get them on and off
easily by trapping between knee and tank to quickly wipe glasses or such bare handed tasks underway
If there is available electricity after the jacket liner (aftermarket alternator etc.) then next would be heated grips
in addition to the mittens
Learn not to actually squeeze grip the grips unless necessary - just rest palms on grips for most of ride
this will keep hands warmer inside mittens wiggling fingers etc.
Heated gloves add a complexity and lack of easy removal and reattach underway that I am not willing to live with.
Tried them and hated them compared to good synthetic mittens with modern insulation and thin leather palms