Re: Blazer 50
The last time I checked on the exhaust issue with the youth mini market, the only US Forestry approved spark arrested exhaust was found on the Suzuki products. If it does not say US Forestry approved, it is not!
On the power issue, you must remember that the 50cc models, including the quadmaster and the Blazer, must not exceed 15mph to comply with the CPSC guidelines for a 50cc atv. As your rider learns to use the machine, there are many many mods that can improve performance (one step at a time).
Another thing you might consider, look at the 90cc models. They are identical in every respect except a few internal engine components and the tire size. You can get a nice set of aluminum rims and 16" performance tires for the 90, use the throttle limiter and have room to grow without needing to purchase so many performance pieces next week.
On the hand lever issue, Blazer has always had a problem with the large format controls. Kasea and a couple of other youth minis have made the controls smaller (Kasea also added a foot brake just like your big machines).