I'm just getting into homebuilding as well, but have been following developments on the electric front, because I believe it's the only way I'm going to be able to fly in an affordable manner. (Also, it's "green," which I'm all for.)
First, your motor requirement is going to add some pretty impressive weight. The "typical" thing to do in that kind of power range is look at motors used on electric vehicles. However, your HP requirement is pretty dang high. Google reveals that 200HP is equal to about 150 kilowatts. If you only use that amount of horsepower for very short bursts, then you can "overdrive" a lesser motor with more electricity to get it there, but at the cost of having potential motor meltdown. Note that existing electric motors will typically be listed at their maximum continuous output, rather than peak. At any rate, there's a lot to look at there.
From what I've seen, battery tech isn't quite there yet either, and is largely the limiting factor.
My opinion is that there is tech out there, but it's not feasible with today's tech. The Sonex folks are working on an electric aircraft with their ESA and associated motor and battery tech, found here: http://www.sonexaircraft.com/research/e-flight/
I'm thinking that is probably has the most promise of things still coming around the bend, but unfortunately you can't even start building one right now due to the airframe still being worked on. The weight characteristics will almost surely be different than a traditional aircraft, so some thought has to be put into this. Also, efficiency is KEY. For the Sonex project, they have two main ways of dealing with it, from what I've seen: make the airframe more like a glider, and tune the (brushless, computer-controlled) motor.