I like the concept you are going for here, i went for a little easier first time out doing this. Took the lotus 7 design and making that an EV.
The higher voltage you go, the lower the amps you will need to maintain that speed. So the lower discharge on your batteries. I have planned on 144V (12x12V), though may drop it back 120V (24x6V) to give better discharge.
Down the centre line is not a bad idea and allows you to drop the passenger sitting hight to really low (from that drawing) and so drop the hieght. Fromt drawings (lines wise) it looks like ur going for something like taller version of the birdcage;
2005 Pininfarina Maserati Birdcage Concept.
Good luck with the build! I am interested to see how i goes as my #2 ev build is going to be a closed body marathon runner. 7 is short blats only.