Decide exactly what you want in a hack. Compare those elements to MG core. Make a short list of things you will need to create from scratch, and the things you will only need to tweak/rename. 70% of MG ought to simply translate over into your hack with very minor (if any) alteration.
As a part of deciding what you want in a hack, determine who/what the group/agency/company is. Is that group a suitable fit for a Mouse Guard-like group? This is key. If they have no raison d’etre and if there’s no “us against X” (the world, the forces of Y, etc), you can’t really continue and expect the hack to work. That group ought to be marginal, or somehow special but a serious minority. In your case, are the airship people like the Red Barons (or whatever the Final Fantasy airship commando force was)? Is that unifying enough? Is there enough meat in their situation as a group to actually allow a fun game to occur? If yes, continue!
The other hard part is having 4 Hazards. You could have Science, People, Corrupt Government and… I dunno… maybe Weather would matter, but it feels really weak. You need 4, though.
Then just steal steal steal. Seriously. Do not reinvent the wheel. Just rename if need be. That said, have a few unique elements. You’ll need skills for piloting and running an airship, for instance, and you’ll need a new conflict type, Aerial Fight or something. You’ll need gunpowder rules and such, as well. Perhaps Steam Scientist is your Loremaster skill (where you can use it to defeat larger constructs or “creatures”).
When it comes to Nature, you will have a bitch of a time. For this kind of setting, I’d actually dump it completely and save yourself the trouble.