It's a really fun idea! Our eternal discussion was always rear- vs front-wheel drive. My buddy wanted to make it rear-wheel drive, so you could still do wheelies on it. I wanted to make it front-wheel to avoid crazy understeering and trike-tipover syndrome. We discussed making the front suspension similar the Honda Gyro 3-wheel scooter's rear wheel suspension, so that the two wheels never left the ground, but one could still lean over to combat g-force. Never quite worked out the theoretical kinks.
almost an enclosed 3-wheel bicycle with a little diesel motor
Here's a pic of our kid-commuter.
Internal 3-speed hub, friction, friction brakes and
front disc brakes for the hevy loads and downhills. We used this a lot, but now the boys want to bike themselves. I've been tempted to outfit it with a Stokemonkey drive.