its fair to include McBuckets in that group as he was a PF in college and is a tweener with some inside moves and physical scoring
The difference with McBuckets is he is not a natural big man. He's not a good enough rebounder or defensive player to be effective in that position.
I'm thinking about players who are big who are dominant against most other big men yet have qualities that typically only smaller players possess like ball-handling, three-point, shooting, and facilitating.
Portis and Mirotic have the potential to be in that category, and that is extremely important to the Bulls' future. Portis is showing himself to be a great rebounder andcan already somewhat hold his own on the defensive end. Mirotic has ways to go in terms of defense, but he can average a solid block per game and is a sufficient rebounder, while stretching out his defender all the way out to the three-point line with pretty good ball-handling ability at his height. McBuckets is a perimeter oriented player who relies on finesse. It doesn't mean that he can't be an effective four at some point, but I don't think you can rely on him to play at a big position against every line-up or for every minute of the game. Especially if you're worried about rebounds and other intangibles needed at the 4 spot.
If Mirotic pans out to be anywhere near as valuable as Mehmet Okur was, I'd take it. If Bobby Portis develops into HALF the player KG was, I'd take it.