Let me preface this by saying I'm loving the game so far, but I foresee an issue with a lack of content in the interim between campaign releases. Additionally, there have been requests on the forum for some kind of melee tutorial as many seem to be struggling to understand the flow of CQC in the game and the rock-paper-scissors nature of it.
With this in mind, I would like to suggest a small-scale, low-cost addition to the game that can be cobbled together with mostly re-used assets.
It would be easy enough to create a one-on-one arena using the map where players are teleported to during the final phase of The Enemy Within in the Alien Myths campaign. Only a basic backstory would be required: that you are playing mirrored shadow versions of a chosen raider, much like the actual encounter in the final boss fight of the campaign. The set up is that you are fighting "mano a mano" to decide the most ferocious antagonist to go out there and defeat some raiders in the name of the almighty Uras-Beherit, A few lines of dialogue from the man himself is all you'd require to provide some context.
This concept would be simple enough to use as an introduction to melee. That said, it could also be stretched into an additional source of content for antagonist players, considering the queue times are currently far too long. You could either keep the above scenario, and turn it into a ladder or tournament system where multiple antags are pitted against one another to duke it out, and the last man standing is awarded stigmas. Alternatively, a larger arena could be created and players could have a free-for-all with as many characters as the engine can smoothly handle in one map. I would assume 8 would be a safe number in a simple map without much detail. Obviously there are issues here where certain raiders, such as Lycus, are better in melee combat, but having everyone play the same character would even things out. This would still fit within the established lore.
I do definitely feel that antagonist mode needs some kind of supplemental content, particularly because the queue times are so heavily weighted in the raiders' favour. However, there's a consensus that many people don't enjoy the mode for varying reasons, but it's a strict requirement for weapon and lore unlocks. Instead of removing the requirements, padding out the options available for ranking up would greatly improve the situation. Having an extra "mode" to queue for and earn stigmas with as an antagonist would greatly reduce frustration and queue times, I would hope.
TL;DR Use existing assets to create a melee tutorial for beginners, and adapt this into a full scale additional mode for antagonists to queue for and gain ranks with.