I have a few ideas, but TW people are kind of thrifty and I don't think you'd sell many of them.
-A nice bolt on bracket to mount a Trailtech Vapor computer in place of the OEM instrument units. Something super sanitary.
-Brackets to mount Trailtech Vapor speed sensors to both disc and drum brake bikes. There's no sanitary option for drum bikes currently
-Billet aluminum footpegs. Something nice like IMS, but aluminum. They sell them for the biggies like Teneres and other higher dollar ADV bikes.
-Adapter brackets to put other oversize tanks on these bikes. Seems like the threads covering XT tanks and the like all use various handmade brackets.
You'll notice a trend in my ideas. I like sanitary stuff. I personally won't do a modification until I'm confident the final product will look absolutely factory when completed, whether using my parts or bought aftermarket parts. That's why I haven't bought one of your oil cooler adapters yet. I'm still trying to figure out where to put the cooler to make it effective, well protected, and look factory quality.