Would this engineering concept work?

I read once that the reason behind the modern trend in cars of engine downsizing in terms of cylinder count is thermal efficiency. A 3.0L V8 will lose more heat than a 3.0L V6, all else being equal, because it will have a greater total cylinder surface area. Because more heat is lost, less chemical energy is being converted into kinetic energy, efficiency is lower.

So why not use the heat given off by the engine to generate further power? What if the water jacket, which is already built into the engine for cooling, were hooked up to a small steam turbine, which would then be used to charge batteries as part of a hybrid set up? F1 this year is already using the MGU-H to recover heat energy from the exhaust, so why not recover engine heat also? Is there a reason why this may not be a practical solution?