anyone string on a 17" rear rim?

I know one with a 17" but the whole rear end is replaced, it's not a relace to original hub. Plus there are all the German bikes with 7" rear wheels.

You shouldn't need longer shocks if you want to stay within restrictions of your fender well and swingarm (keep the approx same radius), you are looking at 140/60R17.
How about cast wheels of old Suzuki GS series? I believe they were 17s. You will have to put some work into it to fit the disk brake caliper. Maybe also new spacers. Belt pulley should fit instead of the sprocket without mods.

Way too much tire IMHO

For width reference, this is 160/60R15 on 4'' rim:



And clearance left and right:





Shows how far you can go with stock swingarm and belt

there are some 95/5 on/off road tires, very good for most street conditions and excellent for the occasional wet/snowy or dirt road.

Motard tires, dual sport, etc.

string and true a wheel i can do, but lathe work no, i could do if i had one, which i don't. so that removes the cast wheel option. however,  the thought of a gs500 entire front end to quicken the steering might be interesting. the ls650 upper triple clamp denies raising the forks in the stock assembly.