That isnt how the NFL cap works. Bonuses are amortized. Salaries are not. Player's also dont defer compensation in the NFL; its a much more regulated environment.At some point the NFL just divided the total compensation by the number of years for the cap purposes. It would be extremely easy to legislate if that is how the CBA parties wanted to proceed. As noted above they have a formula for dealing with this, so at most the Ohtani contract, by taking deferred compensation to such an extreme, might prompt a change in the next CBA.
I guess if you really wanted to get rid of deferred money then you could, but the problem is then ohtani just signs for 10/460 or whatever. He isn't signing for 10/700 in that environment.