Welcome Kymco Owners!
Some of the 50cc tuners on here may have more expertise on this.
As a retired 2T tuner, this sounds like totally nuts! Much easier, and WAY cheaper, to sell the tiddler and buy something bigger.
The motorcycle [licence] costs an extra $80 a year.
LOL! Swapping engines is going to cost you way more than $80/year extra! A 2-stroke will likely last not more than 15,000km, then you'll have to buy a new engine. You might get 30,000km out of a 4-stroke. Moving up to a bigger (longer lasting) engine engine might be a whole lot cheaper in the long run.