I think you missed what I said, let me repeat myself: "Fixed Fuel" Rule
I don't care if they develop a V100 engine, each single race they can only use 1 tank of fuel 1/2 size of what they are using now. I never said the rule is to save money
If your restrict fuel usage, less fuel will be burned. See what I am getting at?? 💡
Yes, but developing a new batch of engines will see thousands of hours spent with engines running at full power, with lots of engineers considering adding another nanosecond of delay to the ignition.
And after a year or two of experimenting, the whole grid will return to V10s, which were the previous best configuration under the open rules, and are probably the best bet now, as well. And then, teams will keep spending hundreds of hours and thousands of gallons trying to save some more fuel, extract some more power, or improve the balance of the engine. And if you allowed turbos again, it would take them approximately five minutes to become the norm - and after a short while, everyone will return to V6 Turbos.
Take, for example, McLaren's 1988 car. The FIA, just before banning Turbos completely, decided to set a cap on fuel-consumption - so the Honda engineers had to spend lots of testing-mileage to get the V6 economic enough to prevent late-race retirements.
Even a potential Mazda team would rather have a competitive F1 engine than a rotary, if pistonless rotaries would prove to be less powerful/reliable/economic. On the other hand, rotary engines are "so thirsty" simply because on everyday applications, they lack torque in the low revs, and need a good thrashing to get going. I assume that won't be the case with F1 cars, who will already be going at 19kRPM and with just 500kg to carry?