Just as Covid has caused extraordinary rules for all companies so it will be for the NFL and it will go well beyond a reduced cap. The NFLPA is going to demand some rules adjustments to benefit their players since FA money is going to be limited, and because top end vets are going to be the first to go on many teams trying to make the reduced cap work.
What they'll do is anyone's guess. But PSJ Ram is in the right ballpark imo. It will probably involve changes in how certain existing contracts, and certain of that team's FAs, are going to be counted against the cap. It may also involve allowing teams to push some amount money that is over the cap into the following year(s), in a similar way that unspent cap from current year can be somewhat recouped in the following year.
I think the owners will resist because I think overall a reduced cap is something they see as a net plus.