takegawa engine or the Daytona + a kpipe would be a Grom killer. The Takegawa is Japanese made, 148cc, has efi and a slipper clutch.
the Daytona 190 is also designed in japan and produced really nicely in China. It's carbureted and doesn't have a fancy clutch, but it puts out a clean 26bhp.
a $1,200 kpipe + a $1,200 daytona is cheaper than a grom and puts out 2.5x the hp for the about the same $ (edited)