I think having radio chatter between the snowspeeder pilots during the defence of Hoth could be an interesting addition. it would definitely give it some extra life and energy (on top of what is already there).

I think if there was any dialogue to be added with the Stormtroopers it would be akin to someone saying "Yes sir" when given an order, ie. something to remind us that there are human beings inside those suits. Even then, I can't say it ever bugged me that the Stormtroopers never really said anything in EMPIRE.