Of course he wanted it to be faster. I'm sure he wanted it to get better fuel economy and a better air conditioner. Everyone who makes a car wants things to be as good as possible...but they didn't make performance a priority. Its not like you couldn't get a decent engine in 1981. Hell, the Esprit of that era, which is what the DMC12 was largely based on, outperformed it by a f*cking mile, and that was a 4 cylinder.
The difference here is that, in reality, they sacrificed the powertrain so they could dump a huge amount of money into the design, the stainless steel, the glue-on panels, all that useless shit that made the car look super futuristic but perform...rather badly. The chassis was massaged by Lotus, but an actual Lotus, even a cheap one, like an Elan from 20 years earlier, would rip this thing apart.
The thing is, there have been dozens of failed supercars since the DMC12, and we aren't talking about them. Why? Because they didn't have such a distinctive design. We remember the car to this day because of that, and really that was what doomed it.
Seriously, steel panels glued onto a plastic body...WTF? That is the worst of both worlds. You have the weight of metal but the rigidity of fiberglass. The Esprit just had...the fiberglass, no metal bling glued to it. Makes a lot more sense to me.