IF Gunner is as good a pocket passer and quick deliverer and accurate long-baller as everyone would hope;and
IF Everett steps up his game to more Tyrod Taylor-type scrambling and occasional running efficiency, which Kelly is relaxed about; then
I could easily see the two of them getting into a psychologically comfortable space with roles like: Everett is the starter and Kelly sees how he rolls, but when it's obvious that the other team is really vulnerable quickly over the middle and to the bomb, in comes Gunner with his height and speed decisions and bomber precision.
That scenario means nothing if it turns out that Gunner can't do these things, which are unproven elements at this time.