I also think it would be interesting to hear principal players in orchestras use similar instruments on most principal parts, unless they are obviously E-flat alto trombone parts.
What if...
1st - .580" - .510"
2nd - .525" - .550"
3rd - .562"+
Everybody plays Bolero on their giant trombones, and it really doesn't sound like a trombone. Plus, there's all that high/loud stuff after the solo, and it's sort of an endurance challenge, whereby I doubt that Ravel meant it to be.
I have a music director with very good ears who often asks for more from the trombones. I suspect he's trying to get more trombone characteristic sound, rather than actually more volume.
I guess it's just as difficult to lure them away from their giant equipment as it is to lure us away from ours.

troll...??
It's up to you to decide.