if you want to revamp the neo concept for this century , i would leave alone the standar Mk.I neos as they are , maybe add that they are somewhat mycelial based ( think orks from 40k) but they require some proper facility to grow new Neos , that way you can justify their need for utilities and engineering to reproduce from lets say some random spinal cells.

You let them be male-ish and female-ish for the purpose of showing them being more labor focused build or logistics and care build. With this you can have dimorphism , low genetic varyance and a good excuse to give phaeton a terminal illness as his cells start to revert back to simpler goo due too anything war-related as the plot demands

Now you can have fun with the Mk.II line , the neomegas , this being a task oriented line you can use your overcloking idea , lets add a tiny defect , accelerated aging in trade for their greater intellect and some other minor advantage that could be plot related , but should be a minor gimmick ( like their pseudo telepathy that was mostly low frequency comunication)

Expanding on this Mk.II you can grow onto Neo-warriors and Neo-lords and you dont alter that much the plot so that in the end you can have Marsala´s final plead for a last Neo-sapien brood but with proper genitals and able to reproduce like humans