In answer to your questions,
1)Yep the engine is a bit exposed.A hugger and a front fender extender are a must.Huggers are available now and Pyramid Plastics are on the case for the front guard.Most of the spray seems to go over the front cylinder.I have used mine in all weathers and it still cleans up well.Its a longer job to clean it tho.There are a lot of nooks and crannies to get at.
2)Belly pans,hmmm,not got one myself but I guess that it would stop a lot of dirt and road muck from sticking to the crankcases.
3)Power,
As you have realised,a Multistrada is not as powerfull on paper as a VFR or an ST4.On the road tho,its a differant story.The Multi is blessed with a lovely torquey motor that makes the bike deceptively fast.In fact some of the guys on the BHC rideouts are astounded just how quick you can go.Its only at the very top end of the rev range the motor gets a bit breathless."On a private test track"

Ive had 131 sitting bolt upright and 138 tucked in.Thats fast enough,innit!
BTW,another essential item to purchase is the Comfort Screen.The standard item is too low and the wind blast makes fast road work very uncomfortable.
4) Tank range,150-160 miles.
5)I cant comment on the centre stand as I have'nt got one.
The footrests are fairly low and I have scraped those.Some serious riding has seen the exhaust guard and rear brake pedal on the deck.Normal riding I only get the edge of my huge size tens down.

The Multistrada is a great bike and I cant stop grinning every time I ride mine.
