: What's up with the skulls?

Cheap easy-to-draw pathos, most likely.

: (I've been playing Arkham Origins...) When the
: skull is displayed: quick fire BatClaw to rip it from it's casing and that
: frees the hobbit from mind control. You get achievements for freeing X
: souls. Free 100 souls in spops and get the SoulHunter achievement.

... Having not played any of the Arkham games, I have not the foggiest idea what you're talking about.

: On a more serious note: I take your point about failure of execution but I
: wonder if the Promethean ideas were innately unexecutable. Could anyone
: have sold those ideas through game play?

Good point.

Watchers and Knights are the same soul:

Visually, the connection between Knights and Watchers could have been enforced with a better summoning animation. What if the Watcher, when not deployed, was visibly integrated into the Knight's armor?
Also, eliminate the face on the Watcher. Sure, nobody knows it's there unless they look at still images, but the fact that Watchers and Knights each have their own face supports the idea that they are separate entities.

When a Watcher is destroyed, maybe a part of it should return to the Knight, or the Knight should make some effort to reclaim a leftover 'spark'.

When it comes to unit behavior, Watchers should stick close to Knights. Really close. Scouting is probably fine, but when the bullets fly, the Watcher should always be close enough to provide support.

This would require nerfing the Watcher's support abilities, but that needs to happen anyways. For example, when a Watcher intercepts a grenade, the grenade should be surrounded by a bright, glowing stasis field. Shooting that field should detonate the grenade.* Similarly, if a Watcher has to resurrect a Knight, then its shields should drop.

*If this already happens, then the target ain't big enough.

-Watcher chatter is when they're spying on you.

Visuals should support the idea. Give them some sort of search light or laser designator to use on patrols, and have them highlight the player.
Additionally, the Watchers can use this light to examine Human and Covenant equipment. It would be like seeing Engineers examining stuff in odd corners of New Mombassa.

To support this with gameplay, it all comes down to encounter design. If the first thing the player encounters is a Watcher, and it's shrill chattering sound calls the attention of a bunch of Knights and Crawlers from across the map, maybe the players will get the idea that "Oh, it's sending up an alarm". After that happens a few times, the player will see Watchers following him and hear them making the same noise, and realize that he is being spied on. Meanwhile, other Promethean units break off and regroup.
Ooh, maybe when the Watcher is chattering, Crawlers could attack en masse and run in formation! They're so much fun when they do that.
Well, at least that's more fun than picking them off one at a time from their hidey-holes.

However, this requires levels big enough to hide in. Something like Winter Contingency, but Halo 4 never had anything this size.

I don't think any of the above could salvage the Prometheans, but it would be a lot closer than what we got.

: But 343 didn't even manage to sell the idea through cut scenes.

Or quick-time events!
/joke

: They had to
: tell us what was going on via forum postings and interviews. You can
: enhance your stories via social media but you shouldn't be telling them
: via social media. That is a failure of writing and/or execution.

Why not? Y'all let them get away with it when it came to Legends.