I think that one partial (and quite unlikely) solution for ever increasing costs in F1 would be simply limiting how much power engine can produce. It would also mean that there wouldn't be much difference between different engines making field somewhat even, there would be some variance between driveability and fuel consumption for example but engine could hardly dictate the successors. I suspect that some big car manufacturer don't want to make race engine that is dynoed by FIA before sealing but I do hope that with right rules there would be enough interest for engine manufacturers.
I know that limiting power sounds bad but in the end it's just one more line in big list of limitations, fuel amount, weight, width, etc. Is it a limit that takes something away from the sport? And if limit is ok where it should be put?