Well, if the Insight is nearly sold, it sounds like you've made up your mind! May I recommend the following linkage?
Endless-sphere.com • Index page
There probably isn't an electric variant-whether Kit-built or DIY-that these folk haven't tried. Also, if you take deathtrain's advice and go with liquid fuel for range, then-
Motorized Bicycle Forum | MotoredBikes.com
-have pretty much tried it all in the combustion/compression engine department. In addition, just for kicks, you could try these guys-
Hank Palmer's Steam powered bicycle and Robert's Style Boiler
Kimmel Steam Engine Collection: George Nutz Steam Bicycle Engine and Boiler
....yes, there are steam-powerd bicycles out there.
Best of luck-and if I ever get my new 8'x8' Workshop up and running, I might try my hand at a simple friction-drive wooden recumbent this Summer, just enough power for hill-climbing assistance. I suspect you'll finish yours first, what with the Insight leaving soon and all...
One more link for luck-
Steve's Recumbent Bicycle Share Project - home recumbent bike builders
-just in case you decide to try the DIY route on the frame too!