I love the idea of smaller (lighter) bikes.
(Currently ride a vstrom 650).
However, at 260lbs (and losing - 20 pounds in the last three months) I worry about the suspension. I am also 6'4" tall so that might be an issue for me as well.
Even when I lose the remaining 45 lbs I set a goal to lose I think I would still be too big for most smaller bikes. I am thinking a dual sport like the CR 250 or WR might work with some spring/shock upgrades.
I like the looks of the GROM - the only non dual sport smaller bike I know of that will be available here. (No counting the Rebel and Suzuki's 250 street bike which both seemed to small for me). But I am sure it will also feel like a mini bike due to my height.
I was in Italy last week and saw several "full size" bikes with only 125CC engines and even a few 50 CC bikes that were full size. Of course, due to our licensing and insurance differences there wouldn't be a (need) demand for those here - I wish we could find a way to import though!