The 20mph limit is slightly disappointing, but I could live with it. I've looked into products like Flykly's Smart Wheel, and the Copenhagen Wheel, and the latter actually appeals to me if I could get my hands on it, but I'm leaning toward just assembling something myself.
vskid3 or ME_Andy, might you recommend me a specific conversion kit? Two features I'm interested in are regenerative braking, and throttle-less design (like in the above two products, so it feels more like a normal bike) - are these reasonable expectations to have of a cheap conversion kit? I'm also rather small and light, but live in an area with fair sized hills. My acceleration expectations are low, but getting closer to 30mph on level ground would be nice. I don't mind having to shift and/or work a little bit.
I'm thinking about grabbing a beater bike for now, and beginning construction of a trike, based on one of these two sets of plans:
AtomicZombie - The Warrior Recumbent Tadpole Racing Trike
AtomicZombie - The StreetFox Suspension Tadpole Trike
^ I'm going to call around and see if anyone around here can do aluminum welds, as I have tons of scrap aluminum laying around.