So I know you guys aren't going for 501st, but here's a comparison of the Jango Arena pack and the Bo Katan / Nite owl pack:
The Nite Owls, most of the grunts (including the Airborne), and even the Shadow collective use the one on the right, albeit painted differently. Occasionally you'll see the long topper if they're using the rockets to fire at someone, but more often than not it's the stubby topper.
The Pyro and later Pre Vizsla use different packs than the one above, but none I have seen use the Fett style pack. Do you have screen grabs I'm not aware of?
Once again, not trying to stick a thumb up at your work, because it's impressive to say the least, but asking and commenting more for personal knowledge!