As a lover of little fun things, I should be sweating for one of these. but there is a problem. Itty-bitty 2-smokes. If such a machine were available with, say a 200cc 15-20 hp 4 stroke, I'd buy one today.
It's not that I hate 2 strokes - I race a KTM 200EXC, but they don't make good street machines. There is also the problem of size. I'm built like MO's esteemed bossman, and although I could see loving a Derbi for a while, wringing its neck every time I want to get away from a stoplight would get old.
Rumor has it that the japanese companies are going to start doing to the 85cc MX class what they did to the 125 & 250 class, meaning 170cc liquid cooled, four valve 4 strokes are coming. These motors would make ~20 hp and weigh ~50 lbs.
Imagine one of them in a Derbi-like bike. Sign me up right now and I'll sell my CRF150F soon-to-be-dual-sport-motard.