Interesting idea, but I regret to say that I can see some flaws that may well cause your project a lot of pain and grief.
First off, you've chosen an almost off-the-shelf chassis/body combination that was designed for a high power motor. It's not optimised for low weight, low rolling resistance or low drag so you are starting with a fairly poor basic vehicle, in terms of making an efficient, low fuel consumption car. There is a good reason that successful hybrids tend to be light and aerodynamic, with low rolling resistance tyres and low loss transmissions.
Secondly, how are you going to tackle the IPR minefield? Several major motor manufacturers have effectively stitched up the majority of hybrid drive topologies with patents. Toyota, for example, have a stranglehold on the very simple, low loss, parallel hybrid drive they use, that stops pretty much anyone else using something similar. Similarly Honda have some strong patent protection on their parallel hybrid drive. When it comes to series hybrid drives things get more complex, as the IPR is scattered around companies like GM and some heavy industry manufacturers who use series hybrids in things like trains, military and industrial machines.
I'm sure there is room for some true innovation that does not conflict with the existing range of patent protection on hybrid systems, but you would be well advised to get some advice from a decent patent lawyer before going ahead.
