I don't understand the issue with rotational mass and FE. Sure, you invest more energy to accelerate, but you get it back while coasting.
When I studied physics last year and we were doing intertia one of the first things was about a car that had a 2000 pound mass and 1000 pound flywheel. If you invested in getting it up to speed it would take four km to wind down or something. However, you gotta know that eventually you will lose that energy to braking, much like having a heavier car. If you invest in moving 300 extra pounds you gotta stop it sometime and that investment will be wasted.
If I hung 10 pounds on my rims and it didn't affect drag the coasting would probably last longer, but seeing as how energy is not converted perfectly to get the wheels moving the savings wouldn't be there in my mind.