The problem with the 2 big-man lineup isn't Theis it's TT. TT was billed as a great defender for the 4 or 5, a floor stretcher, a better scorer, an upgrade over Theis in every way but knowledge of the system. Well so far TT is a bench MLE player not any upgrade. A two big lineup would work with say a real starter like Turner or Vuc, actual bigs who can bang and shoot the three. I'd put DA at fault not BS because in theory you need a 2 big lineup for stretches no matter if starting. This is believed based on a team with two fresh bigs often still puts up a plus stat against small lineups. You can also go to it for easy offense and rebounding when shots arent falling. Neither guy we currently have protects the paint, stretches the floor, or can score on their own. They don't provide any edge on the floor. Both players can look over matched depending on who they face nightly so they are below avg floor defenders too. So when it comes to 2 bigs it's good when you have thever right players. These two being redundant probably isnt a good idea as co-starters but to have the two both not starting is probably worse.
I say worse because in giving up on a 2 big-man lineup the team then plans on what rotation exactly? Playing Green or Nesmith even more as there are no other wings. Or how about playing Semi and GW more who are terrible over huge stretches of a season and can't stay with guards. We are hoping some how we get better production from deep bench guys in this scenario. The smart play is TT and Theis because despite their flaws they are proven and you have consistency. The real issue then is still substitution with any choice of starting lineup as GW and TL are the backup bigs. Both are undersized and both flawed. In theory we have 4 back up bigs not true pencil in starters. And the wing depth relys on Tatum and Brown staggering playing time choking the offense.
All I can suggest is shorten the rotation. Base starters and subs completely on match ups until DA improves the bench. Right now that is counting on a top 8 players that always plays then situation choices. No starters, no unit subbing. Play matchups.
Top 8
Walker, Smart, Brown, Tatum, Theis
Teague, Pritchard, TT.
Situation players
Rest of roster as no one stands out.