Part of the charm of the S200 (to me anyway) is the simplicity.
2 valve, air-cooled. Not much to break on that.
Not as quick as a liquid cooled 4 valve, but a bit easier to maintain in my experience.
Vs. trying to add injection to that, & getting (at best) a bit better MPG, but still facing the 2 valve limitation I'm with Stig and Iahawk.
Get an injected scoot.
If ya wanna stay in the same category/size and such, the People S150, now available in the U.S., has a bit more power and injection.
Think that'd be the way I'd go vs. trying to redo the S200.
I will note that if a bike's just sitting you can get fun, particularly with eth gas on an injected scoot too.