Doing an EV conversion for a Euro 3 or 4 car is reasonably advanced and involved stuff. Concerting an older classic 1950s-1980s make far more sense, greater benefits are likely too.
IMO, converting cars into the 2000s will be about the hardest of all car to convert. I'm not saying it's not possible but I'd let similar age VWs do the trailblazing bit and economically solve how to integrate things. I think it will only become possible if replacement ECMs become available which have integrated emulators and that is years off.