Certain clubs wouldn't be able to pay them, some of those that already do, will always be able to pay them. Its already like that in some form anyway. The wages of Salah, KdB, Haaland are not attainable by 14 of the 20 clubs.
That's why I think there should be a number, a value stated that you can spend a year. £100m a year, maximum on incoming players. That applies whether you make £101m or £800m. It also isn't reduced by outgoings. If you sell a.player for £60m, them you can still only buy £100m of players that year.
Imo, that would make clubs more sustainable and puts everybody on an even keel regardless of starting point.
Also, an independent in every contractual conversation to ensure no dodgy deals and huge sporting sanctions for tapping up or shady monetary deals.