Great looking DR, in much nicer condition than mine. WHeels look good on the bike
I really like the Ninja / Versys 650 DS build. Would even consider doing one myself, but just too much work for me. Besides, i don't have a garage/ spare money/ spare time to build one. But would be a great bike.
For a 19" front wheel you indeed go with either a 2,15 or 2,50 or 2,75 wide rim.
Then you can mount a 100/90-19 or 110/80-19 tire. Plenty of dual-sport or even knobby tires.
For off-road you would go for a slightly narrower rim, so the rim is protected from inpact by the tire.
You could also use more rain type tires on the current rims for better off-road bite, for instance:
Dunlop Sportmax Mutant
Avon Rain Extreme
SM wheels can work very well off-road. I went off-roading with a friend with a TT-R 600 with SM wheels and his bike was even more stable in loose sand then my DR 650 with the 21/17 Heidenau K60 Scouts!? As long as there is no mud and you don't have to brake to hard, sports-tires work very well.
You can keep the stock rear rim, use tires as above and lace up a 19" rim for the front for off-roading with an aggresive dual-sport tire. And keep a stock front for the sport tires. Selling the spare hub you have could be a start to a new front wheel. There are so many options. Or try and get a spare set of 21/18 tires from another Husaberg?
For me next time i will absolutely keep the standard set of 21/18 wheels with knobbies for enduro riding.
And get a second set of 19/17 wider rims with dual-purpose tires for everything else
Suzuki DR 650 SE 2006