Put a lot of attention on the lobby road so that weapons are showcased on your operators and have the proper amount of light on them.
Not sure how on the radar this is, or even how much it can really be improved, but this rarely loads very well on (old, non-X) Xbox Ones. Probably just an older hardware thing, but most of the time I'll see the rest of my team for like 3-4 seconds just before the match starts, if I'm lucky.
On a more positive note, it seems the fix for operators not loading in Ground War has worked! I'm seeing tons of variety in GW now. :D