When WOTC came out we all know the game added new units, some which were regular units added through out the whole game such as Advent Purifiers and Priests, bosses like the Chosen who would hunt you across the campaign till you put them down for good, some were part of very specific missions like the Advent General.

However there were two Advent units that weren't added into the game properly yet were very much finished apparently according what was left over in not only the game files in the SDK but a lot of their left over data was in the ini files and the localisations.

The Advent Hunter and the Advent Hunter Captain (Called the CounterOp and CounterOpCommander in the files)

The former according to the files would of been an Advent Sniper who was visually a green Stunlancer while the latter was a Captain with a green skin brighter then the General but would use the exact same loadout as the Advent Officers, fun fact this would mean we would actually have the Advent Officer's original name reused since Captain is a name that isn't used by them in the final game.

According the files these Advent units would be similar to the Advent General in which they would only show up on a single mission type, in this case that was the Covert Escape missions, from what I was able to gather the Hunter Captain would of been in the drop ship reinforcements with an additional side objective to kill them that would apparently slow down enemies, not sure if that meant less reinforcements or what.

The Hunters themselves would of shown up as reinforcements, I think they would of been the units that you find wandering by themselves in the mission however they would of teleported in, I put up the animations that they would of seemed to use there.

https://www.youtube.com/watch?v=a4cBU5F40zU

With mods such as Skirmish Mode Plus you could actually select them or you could drop them in directly via console commands, however when loaded their models wouldn't load at all.

The only things that seemed to be missing to make them work and show up were proper models however their textures were still in the files, a model for the Advent Sniper rifle, different stats based on game difficulty, encounter lists and whatever is used to trigger the objectives and special Hunter Spawns.

In the end whether these units were unfinished, only temporary templates or cut out for being unnecessary I do not know without more information directly from the Dev's themselves which would be nice to have.