I will probably get into this next Winter. I will start with the rear sprocket. At 49 teeth, there is lots of room for gearing upwards! But what I'd really like to do is just get a water cooled ZS 300cc or 400cc engine and get to work adapting that!
There's a 4 valve 300cc liquid cooled engine on AliExpress listed at $1,257.25, $640 shipping. They posted a schematic along with many pictures, so I can check measurements on the existing 249cc engine connections to the frame. If it all lines up, the Templar X frame should have no problem handling the additional power.
That price includes a PWK34 carburetor, electrical parts kit(CDI,Coil,Relay,Rectifier). The electrical parts could be swapped out or just saved as a backup. It isn't obvious if the ignition they include has hotter spark then the OEM Templar gear.