Two unrelated thoughts:
1. If given a choice, would Danny rather move Romeo or Nesmith in a trade package for Aaron Gordon? I think he'd prefer to keep Nesmith because he projects as a better shooter, and has shown enough energy and length on defense to mitigate Romeo's advantages. Gordon is not a lights out shooter, so Danny will want to keep as much (theoretical) shooting as possible.
Yeah, I'm with you. Keep Nesmith over Langford if Ainge has the choice. Not just because of the shooting advantages but also the injury problems Langford has had. Too many injuries. I am worried about his capacity to stay healthy.
2. If we are going to trade for Collins (a move I don't like, but can't deny the rumors), I suspect that Danny will consider moving Rob (not to ATL, but somewhere). Love Rob, have never proposed including him in any trade package, but I just don't see him and Collins playing on the floor together. Zach Lowe ran a great article this morning on ESPN regarding positional limits of Collins, and pretty much says what I have been saying all along: Collins is a 4/5, not a guy who can defend wings. (that is why he feels Barnes and Gordon, who are 3/4s, will have more trade value than Collins, although it could have as much or more to do with his RFA status). I just can't envision Collins and Rob Willams on the floor together (but hey, it seems to be working with him and Capella together lately, so maybe it can work here).
I don't like considering John Collins a 4/5. I regard him as an out and out 4 who should play the 4 next to a stretch 5. So I agree with you about the problematic fit between him and Rob Williams.
But the reason why I would quibble with the description by Zach Lowe of John Collins as a 4/5 is because Collins does not defend the interior well enough to be the last line of the defense. So he is ill-suited to playing prolonged minutes there.
I feel like there is a growing area of interior 4s / perimeter 5s combinations in the league that are being ignored because some people (like Zach Lowe) want to describe them as 4/5s instead of out and out 4s who need a stretch 5 rather than an interior 5 next to them. Zion Williamson is another one of these players who suffers from this with Steven Adams (interior big) instead of being played alongside a perimeter 5.
John Collins is an out and out 4 who has an inside-outside game but needs interior space available to capitalize on his interior scoring capabilities - and to do that, he needs a 5 who helps create that space for him by being able to play on the perimeter. That does not make Collins a 5. It makes him a 4 who needs a stretch 5 next to him.