I didn't intend to propose a 4-3 defense. I want the coaches to see if Gary could play 3-4 DE. He's big enough to play that position and it would provide the easiest/most impactful way for him to see the field more often.
Then I would say you are excessively focused on the 25% base defense snaps.
We were discussing whether Gary is a redundancy with respect to the Smiths. So lets start with the assumption that Gary is capable of being a 3-down player, at whatever position, good for a 70 - 80% snap count. Otherwise, the redundancy issue is moot--he'd be just a bad draft pick.
So lets say he is your starting base DE for 25% snaps. That is a non-redundancy as you suggest. Where would you put him for the other 45 - 55% of snaps assuming he's not a bust? The most obvious possibility is he plays 3-tech DT in nickel. This is a common approach in 3-4 defenses with that 3-down player who happens to be the starting base DE. We've had some guys like that--Cullen Jenkins, Raji after they moved him off the nose to base DE. Clark might be that guy sooner or later if they bring in nose tackle for base play.
In any case, let's say Gary is that Cullen Jenkins type guy as you suggest, assuming he is a player. I don't consider that entirely unreasonable. However, he would still not be a redundancy. He'd be taking Z's inside snaps, confining Z to the outside.
When you listen to Gutekunst's comments, after the draft up to now, he envisions Z and Gary interchangeability at Gary's upside, where either could play inside in nickel. Given the fact Gary was a high pick. we can presume he's not blowing happy talk smoke about that projection.
The key problem with your proposal is once you shift Gary to a hand-in-the-dirt player, coaching him up as that kind of player, you've lost your OLB depth. But either way, OLB or DE/3-tech, Gary is not a redundancy at all if he actually becomes a player.
As I already noted, 80% is at the high end of a reasonable snap count for a 3-4 OLB. As an OLB alone, that's 40% snaps on the table for Gary right there. Play him inside in nickel instead of Z and you're already up past a 60% snap count. If he develops to a point in line with his draft spot, you can split those snaps at 75% across the board where you're less likely to see these guys gassed at the end of games.
You know, 1 or 2 down base NT run stuffers are not very expensive. Sign or draft one of those and move Clark to DE. While I would not expect that, it is more plausible than your proposal.