What would you want?
Let's say this, the design team from your favorite ATV manufacturer has came to you and said "We're designing a new 3 wheeler, how would you like it?"
Here's my entry:
Engine: light weight 450cc four-stroke w/ electric start and reverse. Reverse would be a bolt on, removable unit. Quiet exhaust tone.
Suspension: Minimum of 12" of travel front and rear with progressive style springs or Air ride (similar to Fox Floats) full adjustability of compression, dampening, and ride height. Adjustable width rear axle.
Ergonomics: Adjustable foot peg locations and adjustable Handlebar height. Semi-firm seat design. Easy to reach controls w/ a push button reverse and key switch. Hi/Low dual headlights, high resolution tail light and brake light.
Tires/Rims: More modern tire sizes w/ traditional tread designs. Light weight aluminum rims with bead reinforcement.
Most importantly, it would be a KAWASAKI!