What I’m saying is it wouldn’t make the defense “less reliant on filling gaps by taking guys out of coverage”, that’s not how the run fits work, your run fits are completely dictated by the coverage you call. You can call Quarters and have the safeties take the vertical of the #2 receivers and if their receiver blocks, they will add into the run fit. The defense would be max fitted for the run game while also not taking anybody out of coverage. On the inverse of that, you could call a bracket concept where the safeties are playing an inside/out double on a receiver with the corners, but they’re completely out of the run fit. Now, the defense has maximized their pass coverage, but they’re out gapped in the run game and need to steal gaps.
Most of the time, Fangio is going to line the defense in a Nickel 4-2-5 with Wilkins & Sieler both in the interior. You really don’t want to replace either of them with some space eater, you want to keep both of them on the field as much as you can because they’re both effective pass rushers. Fangio’s philosophy is to invite the offense to run the football, he’s going to keep his safeties high pre-snap, he’s gonna line up in an even front with 2 backers and give every pre-snap indication to the offense that they can run the ball. If the offense does run it, that’s fine because maybe the defense stunts post snap into odd spacing, closes the B gaps and brings a safety down in the run fit, the defense has every gap accounted for and the offense gains 2 yards. If they pass, the QB now has to diagnose how the defense rotates post snap and make them hold the ball an extra beat, and since the defense still has 4 guys on the Dline that are plus pass rushers, that extra half second could be a strip sack.