TP, Jvalin. Excellent proposal to get flambéed over. I'll start.
You've been pushing this idea before and I can see the appeal, particularly from an offense standpoint. With Simmons as your main ball handler surrounded by 4 guys who are legitimate threats from the 3-point-line you really put your opponent to the test. Especially in the open court this line-up is extremely dangerous no question about it.
In the halfcourt I envision Simmons defended at the top of the key, while 2 players on the right and 2 on the left side of the court are waiting for their man defender to leave them open, because he has to help in the paint to stop Simmons' drive to the basket. But there's no big to set a screen to play pick-and-roll. You're entirely dependent on Simmons beating his man one-on-one and making the right play. And although that might not be a bad go-to-play at all (look at how good Westbrook has been in Houston after the Capela => Covington change) it makes the team too one-dimensional for my taste.
This extreme small ball concept has started by the very succesful so-called Golden State 'death' line-up of Curry/Thompson/Iguodala/Durant/Green. In my opinion this has become a bit of a myth. Yes, that unit had some ridiculously good ratings, but why did Kerr only play like this for about 10-15 minutes a game? And actually mostly abandoned it in later years?
First of all, that power forward that played center in those line-ups is former DPOY Draymond Green. And while Simmons has become a sublime defender, he isn't used to bang in the post like Green and also Simmons has no experience as a primary rim protector (I believe Embiid is a not to be ignored factor in the Sixers defense). So I really question the interior defense and rebounding when Simmons is your starting center accompanied by Hayward and Tatum.
On offense the Warriors had the Splash Brothers plus one of the best offensive players of all time in Durant. That kind of off-ball threat is impossible to duplicate. Teams where completely overwhelmed when the death line-up was introduced to close games. Defensive schemes didn't work anymore. Panic overall. Media wrote that Kerr kept his best weapon on hand to use whenever necessary.
But why would you not utilize your best weapon and keep games unnecessary close? To preserve Draymond Green as was argued? I'm not buying that. Green was used to bang in the post against fysical players, he is very durable and having to guard bigger guys wouldn't change that much I think. What would matter is that against a legit center, Green would become somewhat exploitable being only 6'6/6'7. On the other side of the court teams started leaving the worst shooter wide open (Iguodala at that time) and lived with the results.
Teams were adjusting to that 'death line-up' and while I won't say that it didn't work at all, I do believe that after the surprise element was gone it became much less effective. Golden State has always played with true centers since then, whether it was Bogut, Pachulia, McGee, Looney or Cousins. And while the game is definitely changing I don't believe that centers will become a dying breed.
Yes, traditional post-ups have proven to be not be the most efficient offense play in general, but guys like Embiid and Jokic are still a problem. The tactics to switch on defense and defend the pick-and-roll has demanded much more from centers, so that's an adjustment that has to be made. But when you look around you see that true centers are still very succesful in the league. A couple of weeks ago Bleacher Report came out with their top 15 centers and I heard Theis wasn't on it, so I was a bit perplexed and felt that he was overlooked. I looked up their rankings and had no big beef with it:
Jokic, Embiid, Towns, Gobert, Adebayo, Vucevic, Ayton, Aldridge, Ibaka, Adams, Lopez, Harrell, Favors, Valanciunas, Wood. (not mentioned: Turner, Allen, Gasol, Whiteside, Capela, Drummond, Thompson, Jordan, Carter, McGee, Holmes, Zubac, Robinson, Howard, Poeltl, Noel)
Simmons at center will not do well against the majority of these guys. The advantage by a mismatch on offense will not offset the presence that you give up in the paint. Doing the dirty work in the paint, boxing out, protecting the rim, setting screens and getting offense rebounds is an overlooked art in the NBA. You see in the draft that there's a heavy focus on wings and guards and that talented bigs end up as a late first. I think it's a current trend and that this will change again.
As the list above indicates there's an abundance of good 'role-level' centers, so the market for centers isn't great and they are cheap to get. From a financial standpoint it makes sense to draft a wing over a big when they are comparably talented. Another aspect is that a lot of superstars lately have been wings (James, Durant, Leonard, George, Antetokounmpo) and thus the narrative is that wings have more impact on the game.
I'm not sure about that, I can well imagine that in a few years Embiid, Jokic, Williamson, Towns, Adebayo, Porzingis, Collins, Jackson Jr, Ayton are all considered top 20 players. And Antetokounmpo 6'11, 242 lb, can easily be considered as a superathletic big. Also with the emergence of Young, Morant, Fox, Mitchell, Booker and Doncic (guard or wing?) it might be that the league will become top guards/bigs heavy and that elite wings like Tatum, Siakam, Ingram and Brown (?) will be very scarce.
Okay, not sure where this is going to. Lots of rambling.
I believe it's a good idea to think outside the box and sometimes an unorthodox plan turns out to be genius, but look at the results so far for Houston (admit: small sample size) after the 'Capela => Covington' trade:
Houston with Capela on the roster, team stats:
33-18 record, PPG 2nd, RPG 6th, OR 2nd, DR 15th, DREB% 22nd
Houston with Covington on the roster, team stats:
7-6 record, PPG 7th, RPG 27th, OR 13th, DR 15th, DREB% 30th
On the other hand:
Russell Westbrook with Capela on the roster, player stats:
26.7 PPG 8.0 REB 7.3 AST 45.8 FG% 23.7 3P% 79.0 FT%
Russell Westbrook with Covington on the roster, player stats:
30.8 PPG 8.2 REB 5.5 AST 53.8 FG% 37.5 3P% 72.3 FT%
Simple conclusion: the trade worked to help Westbrook score much more effectively, but it didn't help the team overall. Not only the DREB% dropped to dead last in the NBA, but the OR plummeted from 2nd in the league to average at 13th. And that while Capela is far from a special player on offense. A center that sets screens and is a threat in the pick-and-roll adds a dimension to an offense that should not be overlooked.