Ah... the modular approach. A lofty goal, indeed. Still, you have a better chance of getting there than most.The platform is supposed to have modular sub-frames to accommodate multiple motor, controller, and battery drive solutions. We are in communication with a number of the more prominent EV drive companies, and we will specifically design to at least 2 providers, while simply trying to stay modular enough to potentially use others.
I don't know what motors and controllers you're looking at, but right now there is absolutely no contest between AC and DC technology when it comes to power. Some here may say I am biased because of my association with Evnetics, but that doesn't really change the fact that the statement is true.
Regardless of the motor/controller technology you choose, you would do well to consult with an experienced vehicle conversion shop, especially one that does high-end conversions (my very biased suggestion here would be Rebirth Auto), and the infamous Jack Rickard - http://www.evtv.me/ - even though you might need a flameproof suit. He has built a couple of Beck Speedster "356" kits with both AC and DC controllers and is working on an AC Cobra kit. In short, he has already done exactly what you are proposing to do and could be a very valuable resource, assuming you don't get him all riled up, that is.