I've owned 700lb and 300lb motorcycles that could be held leaned over at 100mph. I think wheel size contributes more than the weight - but the wheels are very similar to my old Burgmans'. Suspension components come into play - but I don't think the shocks and forks on the Burgman were any better.
I think the biggest factor is something we can't change. The XCiting (unlike the Burgman 650) moves the engine with the rear wheel. So the suspension has a harder job to do, and more dramatic changes to the center of gravity when leaned over hard. The XCiting also has a much lower weight capacity. The Burgman 400 is built much like the XCiting - but it weighs less.
The XCiting's engine, wheels, and brakes can handle high speed travel - and better suspension components may help - but I think it will never be able to smoothly handle 70mph sweepers or or other road conditions that conventional motorcycles (or a Burgman 650) can handle. Oh well...