It's going to be near impossible to find an 'off road' tire in 16" sizes. (A quick look, and I didn't find anything....) The 17" swap is not too difficult these days thanks to the influx of newer generation Ninja parts that will (mostly) bolt right on.
I've spent the last 2 weeks doing just that - though not for dual sport tires - and am waiting on a few parts to tie up the loose ends. Should be done later this week... I don't have a thread up currently, but will be posting one within a day or two to help other members along the same route, if they so choose.
If you're really going for the scrambler thing, you may want to look into mounting some handlebars rather than using the stock clip-ons. Good leverage via wide bars is going to make a huge difference in how the bike feels over loose terrain. Another member here has already done that. See his thread here --> (
https://www.ninjette.org/forums/show...=117957&page=2)