Sandtroopers there are at least one without a pack in ANH. But there are no HWT without pack in the game it's based on. Sure, you can make a deal with your local garrison and or EC. But it's not really fair to say that it's universally optional (which is what it is when you say it's not mandatory).
Secondly, how will the event requester know in advance that you and your buddy will be HWT's and do they know the difference? You're leaving a lot of responsibility on the requester in order to create a void of uncertainty where it could be interpreted as an ability to troop as a mix-n-match of costume parts.