While you're considering front suspensions, include the VW Superbeetle's McPherson struts. Mine weighs 1980lb with 840lb on the front, unladen. That on the front of a trike would imply ~1260lb total.
The lower control arms are separated by about 6-8". If those were brought together on a new frame the front track would be 3-5" narrower. The McPherson struts need a connecting strut at the top, but in a typical kabinenroller layout (driver's feet close to or ahead of the front axle line) that would be positioned behind the dashboard or at the base of the windshield.
Your scooter engine can cantilever off the back of the seatback, but then what do you do for a pushbar/rear bumper?