Dude listen. I'm not saying Green should play because he DESERVES it but because we need to know if he's worth giving a contract to at the end of the season, cap space dictates everything and we need to know if that millions of dollars is worth investing in a Gerald Green. The only way to know is giving him a chance to show off his abilities to the coaching staff in real-game situations not just practice. And 4's and 5's are interchangeable just ask Amare Stoudemire, Al Harrington, Kevin Garnett, Rasheed Wallace, Dwight Howard, Chris Bosh, Pau Gasol, Mehmet Okur and Lamarcus Aldridge.
Luis Scola is going to be playing some 5 now, out of need. He's the only guy with post moves. He's only 6'9 though (if you believe he's that tall). Did you see him get abused by the worthless Bulls C Gray??? Now imagine running through the Western Conference's inventory of Cs. He won't be able to take that pounding every night, and play offense. He's too small. Its a big difference doing that 8 minutes a game, and doing it 30-35 min a game. The team is going to be looking for another C.
And all of those guys you mentioned are taller than either Scola or Landry, ranging anywhere from 6'10-7'1. Amare and Harrington played C in a completely different offense than the one the Rockets run, where its get up and down the court. Amare struggles at C, which is why they got Shaq, and why previously they had Kurt Thomas. Not to mention he's bigger (6'10) than Scola or Landry. Harrington wouldn't be playing C in any other system.
All those other guys you mentioned have Cs because they wouldn't be able to shoulder that load. Garnett starts alongside Perkins. Bosh has Nesterovich. Wallace is playing C this year, but is also 6'11. Gasol will have Bynum (not to mention he's 7'1). Aldrich has Przybilla. My only point is there is a big difference between sliding over to play C for 5-10 minutes a game as opposed to starting and playing there an entire game. Almost any of those guys you mentioned would be worn down and/or get in foul trouble. When a team plays a 3G set, that doesn't mean guards and forwards are the same thing. They are just temporary adjustments. The Rockets can't go the rest of the season playing PF at the C position.
But in the end, you are right, we are going to need to push the ball more with a smaller lineup.