Hall of Fame
I'm going to jump in here. My assumption is that the defense has only one elite CB. If they have two, this would be ideal.I almost added your scenario. As a DC facing Texans doing that I would depend on my middle guys stopping David Johnson. As you say, if he gets past front 5 he could score. A good middle stops that play almost every time. I like mismatches but prefer those to be my WRs in which I believe O'Brien is counting on. I like both DJs faking a block then opening up for dumps if needed or planned; with Watson scrambling abilities I see that is best play although draws should be used frequently as a planned endeavor. This was fun exercise!
If the offense has two WR's with elite speed, in the 4.3's, you're going to need a CB on each. But you're going to have 2 safeties giving deep support. If the elite CB can cover one WR, one on one, then that frees up one safety to move up for medium support. But the defense will probably be in a dime package because you need DB's to cover the receivers in the slots. If one of those is a TE, you can be in nickle with a LB on the TE. But if that slot receiver also has good to elite speed, the CB will need help from that freed up safety.
But in all cases, you have 6 players covering 4 receivers. This leaves 5 players covering 7, five of the 7 being lineman. One of the 5 defensive players would be a LB responsible for the RB.
This leaves one safety to leave his receiver responsibility to cover the QB.
Leaving the defense in a 4 man rush covered by 5 OL'men.