Tech Drool Challenge: Build a Better Hybrid

A few friends have aquired Priuses (Prii) over the years. They tend to be die hards. Some have put in the "no gas" switch, letting them keep the car in electric mode. I've read of kits which add more batteries to extend the range.

So here's my challenge: Design a hybrid which optimizes size, performance, weight capability, and range, yet has the most diminutive gas engine possible.

Why? Consider this; if the entire engine of a Prius was removed (and all supporting components; tank, pump, etc), I'd bet enough weight was saved that you could replace it with batteries of equal weight, and perhaps double the range of the original battery. Same performance, double range, with no gas. Plug it in overnight, or while at work, and you're set. Zero emissions (from the car, I mean).

Now, the grid may not always be available. No problem; put in the most efficient small turbine possible. No matter it takes a while to charge; the car would tell you your range before you started the day. And gas stations could offer a battery swap. Need 50 miles fast? $10 for a swap. No problem.

Ultimately, my aim is to optimize a commuter hybrid, which is only expected to go 10 to 30 miles a shot, but have a range of about 75 miles at maximum charge.

Discuss amongst yourselves.