Well, to continue on with my own install here are my learnings:
I measured the yellow/red (Reg/Rec DC from stock KTM that normally goes to the digital odometer) and got ~5.5A output with the battery disconnected. I did this out of curiousity to see what that OEM unit was putting out.
Theoretically there is quite a bit of power from this existing DC circuit (50-80 Watts). I'm not sure what the battery requires to charge, but you should be able to run right off of that though you do run the risk of draining the battery.
I added a rectifier which I purchased from digikey (part number GBPC15005) to the yellow wire that normally goes to the headlight as the AC input, and the brown ground wire to the other AC input. I found I got 7.5A output with this installed.
I put a load on the digikey rectifier and found I got 9-15V. So in total we are looking at 70-110W which is quite good and should be enough for grip heaters and a headlight at the same time.
Anyways, I'm going to continue with the yellow AC wire and use the rectifier I purchased and run a capacitor I had laying around from another project to smooth the voltage. My only shortfall here is my capacitor is rated for 16V so let's hope it doesn't burn my bike down if I ever rev it out and let it scream with a current draw.
I noticed when I measured the current the rectifier was getting warm. So I cobbled together an old heat sink to my rectifier from an old computer motherboard I had lying around with my stash of pocket protectors. Made my own bracket, and mounted to my triple clamp. The other bracket you eagle eyed riders may spot here is for my heated grips switch I made previously.
Remember to fuse the input (yellow wire) of the rectifier! 10A should do it.
The only thing that surprised me is when I rev the bike out, the light dims a bit? I haven't been able to explain this yet.