Thanks for your explanation.
For projects that allow using both CPU and GPU you could still mine with your CPU but that wont be recommended as reward would be much lower, the same that happens with current system. I think this is good because that encourages efficient use of computing and protects Gridcoin against potential PoW attacks by GPU miners.
i share the opinion that tracking flops is not the direction we should turn to. This would turn the balance that we are now having completely upside down, things like crunching with a raspi or so ( even now this is not making any revenue :) ) would then be completely off the table. We would then be in the GPU "mining" corner just like every other POW coin (except them with asics which is even worse :) )
For sure a reward mechanism should reward the actual work that has been done on WUs, the variability and flexibiltiy of all the BOINC sytem is what makes it very complicated to find a easy solution. Thanks alot @sc-steemit for bringing up this discussion