I think the Stelvio has the potential to be an excellent bike. If its a big chunky thing then who cares? All big Guzzis are heavy, and if it has the 4 valve motor the power to weight ratio will be better. Nobody rides these "adventure tourers" off road anyway, except on TV where they always drop 'em. If I wanted to off road I would buy a cheap 125 two stroke, or maybe an XT600 if I needed to ride around the world.
The plus points will hopefully be big comfy seat and suspension for crappy British roads, nice tall riding position and torquey motor.
Guzzi will never sell more than the trendy GS, but I think they can sell a fair few and I am sure it will be more reliable than the 1200GS which has a poor reputation amongst the BMW folk, some of whom are swapping back to the older heavier 1150GS.
Guy