Since, lets be honest, the legion mission archives are horrific at the moment. For a medal requiring so much effort I have a couple of possible suggestions to improve them and make them worth something. Or have a medal requiring an greater number of tasks completed which rewards something like this, it would make the legion mission archives less terrible as its a stepping stone to a better reward.
Possibility 1: Mission Aptitude
When installed, if your legion succeeds a legion mission you gain an extra relic badge.
Possibility 2: Unlocked task
On one of the new missions, best would be on a follow up if the first mission succeeds, there is a task for which the requirement is: Have the legion mission archives installed or the new medal reward.
Possibility 3: Thematic building
Constructs a planetary structure based on the legion mission currently active, costs X relic badges per use and has a 72 hour cooldown.
(These planetary structures would not be avalible from anything but the legion mission archives, Each planetary structure would have different name, image and stats based on what legion mission is currently active.) A bit like the bainair ability but instead of being random it is based on which legion mission or chain you have been assigned.
If anyone has any suggestions for another possibility then feel free to suggest it and if I could have your opinion on which you would prefer that would be helpfull
