As much as I admire the "let them have more engines" idea, saying if they can't afford it they shouldn't be there is the kind of situation that kills series. F1 is struggling to sustain a 20 car grid right now, so proposing anything which raises the costs is likely to have serious negative consequences on the series.
The engine cost per unit is the issue. An IndyCar engine costs £50,000. Am F1 Power Unit costs £9m. That is a ludicrous gap. WEC/F2 engines are similar to an IndyCar engine. The reason F1 struggles for teams is very few have the ability to bridge the gap from another series to F1. If you want to improve F1, improve the show, and improve the prospect of having a sustainable series, then reducing the cost of the power units is a major step to doing that. The current regulations are pretty much written by Mercedes and Ferrari, which allows them to build themselves this insane walled garden where the entire series existant now hinges on Mercedes and Ferraris ability to sell engines to other teams (since you can no longer ask Cosworth to produce something for you), and they've done so by jacking up the prices to the max to get as much return as possible from it.
I too would like to see the teams have more engines. But that doesn't work with the current walled garden engine regulations.