Hey Kusanar! Welcome to the thread. I don't think you're crazy, but I think you may be trying to do rocket science with leggos (so to speak)... making this a whole lot more complex than it needs to be
I see where you're trying to get to with what you want to attempt, but not sure exactly how you can do it... If you want "fastest", the temp will have the greatest affect... mid-upper 80s = fastest, as temp drops, time slows down till you get to about low 60's when things go pretty much dormant. That's why you can put them in the fridge to slow everything down to create staggered "hatches". The other issue is determining sex of the beetle... Not sure how you'd do that, so 10-20 beetles may have an inordinate amount of either male/female... in addition, they'll all be mating w/each other, so there's no way to make the fastest breed only w/the fastest...
Also, with some critters (like alligators and other reptiles, temp affects gender... not sure if that holds true w/beetles... Maybe you'll put 10-20 pupae in a box and the temp will make them all one or the other...

Just speculating/guessing/being devil's advocate

Without getting eggs that are all laid on the exact same day, and eliminating all variables except the one you are working on, I don't know how you can do this. But I wish you the best of luck and look fwd to hearing what you determine.