you can't have both variation and a smaller pulley.. there are different sized rear variator cheeks that came on different vespa moepds, but none of them are stamped, and it's a pretty small difference. nothing too noticeable as far as performance goes.
the malossi case is rad, it's what i run on ciaociao, but you might have trouble finding cdi to fit it and the points version is nearly impossible to find.
single speed doesn't suck any more on a ciao than it does on a puch or any other one speed moped. you have to look at variated vespas and non variated vespas like they are two different mopeds.
the one speed is like a e50 puch where you're going to be fighting to keep awesome low end but can get a much higher top speed than with a variated vespa.
the variated bikes will be fast off the line and rip up to the top speed and all, but are pretty limited on top speed.