Mission Architect: Optional/Alternate Mish Goals
I would prefer simply permitting Boolean operators. So when you say, "Doing X will complete the mission, and also doing Y+Z will complete the mission," we could have (X) OR (Y AND Z).
This would be a very powerful tool for things other than just mission completion goals, as well.
Edit: with Glowies as g, Captive as c, and Boss as b, the examples you list are:
g OR b
c AND (g OR b)
((g AND c) OR (g AND b)) OR (b AND c) (with a multi-operation logic, this statement could be simplified)

A Story Arc mission idea I had before ever touching the Editor in open beta was for an arc in which the Player had the option of completing the mission by either defeating all the enemies inside the base, or by stealthing and simply clicking Objects for clues. Doing either would score the Clue and complete the mission.
I propose a request/suggestion that this be an option given to Arc Creators. Under the Settings portion of the current Basic Mission Goals selections is the radio-button toggle that sets that goal as being "Required for Mission Completion." A second button could be added which makes this goal "Optional for Mission Completion." This would make it necessary for the Player to create another Mission Goal, and the Error message should be triggered alerting the Creator to this.
Once the other Mission Goal is created and also flagged as "Optional", the engine could automatically determine that the requirements for this arrangement have been met, OR, it could be possible for the Creator to make a manual and intentional link between the two Goals, using the same method by which one Goal is linked to another with the "This Mission Goal is created when..." drop-down menu.
Here's an example:
I create a Collection of 5 Urns, and under Settings, select "Optional for Mission Completion", at which point the Errors box lights up and tells the Creator that the mission lacks a a matching optional mission goal. I then invoke a "Fight a Boss" Goal, and also select "Optional". Under the "automatic" scenario, the Error disappears, the requirements having been met. If the "manual" link mechanism is available, I can then enter the Urn Collection's settings and select the Boss Goal as it's matching set, then do the same so that they are pointing at each other.
Now, either way, it should still be possible to create a third Mission Goal that must be completed no matter what to complete the mission. Let's say it's a Free Captive goal. In order to complete the Mission, the player can either (Free Captive and Collect Urns) or (Free Captive and Fight Boss). Either combination wins.
It could even be possible to make that Captive a third Optional Goal. The manual links could be assigned as a "loop": Urns -> Boss -> Captive -> Urns. Manual links could even allow for multiple Optional sets: (Urns or Boss) AND (Captive or A Different Boss).
That would allow even more flexibility for a Creator wanting to make a mission that's more than just a grind or a scavenger hunt, and would almost give them the ability to make logic puzzles!
W4E