Considering the back, shoulder and wrist issues I would be looking at an FZ10 or FZ09. All the power and performance but the seating position you are used to.
But that isn't what you asked, you asked for something similar to the R6. So why not a mid- 2000's used R6. 04's and 5's can be had all day long with few miles for 4K or so. If it doesn't work you can sell it for pretty much what you paid. If it does work out you can keep it, or sell it for what you paid and go buy a new one if that is your preference.
Especially if you buy now in the fall when prices are deflated..make your decision and sell in the spring.