Aside from the usual central Asian how, how about a dystopic strategy game where you have something like an MCV from C&C and move from ruined city to ruined city to scrap up what few resources those places still have to offer?
Could have some interesting mechanics - stuff like:
>"Weak" structures you can scrap/recycle vs. "Strong" structures that you have to leave behind when moving on
>Establishing a defensive perimeter around your mobile base and then packing it up again when leaving, all while the nasty folks know you're most vulnerable doing these moments
>Experience system for troops, maybe even RPG elements if its on a smaller scale.
>If you want to go for something more akin to a simulation experience, make the player worry about having enough fuel for the mobile base and any other vehicles in your fleet
I always found the idea of moving around your production buildings and ancients in Starcraft/Warcraft III something way underused in both the regular gameplay and the campaign missions. Same, to a lesser extend, for the Undead's ability to sell their structures.