How does the GM section address adventure creation for the Battletech universe?
A good question.
I should step back and introduce something they call the "Cue System". I completely spaced on this because it literally is 3 or 4 pages in total over the entire book, and it's potentially so weird that I mostly ignore it.
MW:Destiny is supposed to allow for more Player-driven narrative via this Cue system where the player has license to basically narrate whatever they want into the universe. For instance, the players have full agency to introduce NPCs, describe them, describe the NPC motivations, describe the NPC actions. (Literally, Natasha Kerensky can drop with the Black Widows on top of the bad guys and stomp on them if your player decides to say that.)
In some ways, the system (as written) uses the GM as a rule arbitrator sometimes moreso than a storyteller. The PLAYERS are expected to provide more narrative than in other games, literally with the power to create whole characters on the fly.
It's something that complicates adventure creation, and you have an expectation that your best laid plans will always be derailed as a "feature" of this system (should you wish to play it this way with the degree of player control over the narrative).
That part is easy to hand-wave out, and to play it as a traditional roleplaying game where Players can't create NPCs out of thin air. -OR- you can limit this Cue System to specific points in your narrative, like specific points in the narrative (between Act 1 and Act 2) or when they reach a specific physical location (like a spaceport).
There's an inherent layer of trust involved in this level of narration.
So, adventure design.
It's a sketch system, really.
It tells you to think about theme, and in a basic way (like, courtly intrigue, big hollywood explosion action movie, etc.)
Then you set the overall Mission Objectives (i.e. what your players are supposed to do to "win").
After writing an intro, you set your own adventure Cues and tags... Tags are like meta tags ("House Liao", "Covert Operation", "Dropship Assault"), which contain the elemental aspects of the scenario you're involved in. So, if House Liao is attacking a planet that your players are defending, then "House Liao" is an obvious tag.
Cues are basic questions and ideas to spur the narrative (should your players get stuck)... like "Why does it seem like ComStar is helping them?" or "Why are their Mechs painted plain white?" or "Keep an eye on the Dropship"... and under the Cue system, both you and the Players can construct answers to these cues/questions (with the Tags in the back of everyone's mind when it comes to sketching out details around these Cues).
Yes, you can create extremely scripted scenarios this way, but the intent seems to be more free-form design.
Now... as for making it make sense within the Battletech universe? You're expected to know this stuff coming in, I guess. So if it breaks with the history of House Davion, then you've broken it and it's your universe now.