Simpler, cheaper engines ragged to death every event. Manufacturers make the ICE, a supplier makes the energy recovery for everyone just as they do the ECU. Full throttle all the way, bin the ICE on the way out of the circuit.
Manufacturers still get to differentiate themselves, but all the complex energy recovery is standardised. Costs decrease exponentially.
Fuck it, I'd allow unlimited ICE. Qualifying specials that grenade themselves. Part of the unpredictability you used to have was the cars were constantly under threat of breaking down, this is reponsible for some of the shocks and the minows getting a freak podium or win. IMO they should be run to such extremes that they are on the verge of blowing up all the time.