I would say keep things the way they are. Build interest first then when 20-30 adv bikes are lined up with 690's filling the podium, the rules could be tweaked. The KLR isn't as weak as you would think. A friend would ride his clapped out KLR to enduros, RACE the enduro, get top 5 in DS class, then ride home.
I would agree XR650 is not adv since it won Baja how many times?