Well, so this isn't really a "variant," just a slightly different way to think about the existing rules. A bizarre concept, I know, but the game oozes atmosphere and yet has an explanation completely divorced from the game play. The "theme goal" is to get rubium, yet rubium is only distantly related to the "rules goal" of winning battles. The energizer cards have no "theme" explanation at all.
So anyway, following is a background/theme that I think is a plausible explanation for the game mechanics and can improve the lovely sense of immersion. Some of the card labels don't fit and must be ignored or mentally (or physically?) edited (e.g., energizer, scattered rubium).
You are the Chief Station Officer at a mining outpost on an isolated and inhospitable moon. Several mega-corporations which are in commercial conflict around the galaxy (i.e., serious commercial conflict), have mining concerns on the moon.
Your goal is to aquire enough brownie points with company vice-presidents to manage a transfer to somewhere more appealing, such as any place else there's a company office.
Disparate instructions drift down from above, with useful micro-management from various VP's, advancing their notions of how best to sabotage the competition and highlight their particular tactical brilliance. A senior Officer such as yourself would not expect these instructions to be consistent, or even coherent. Yours is not to reason why. Every time you can report that a VP's nifty idea of the moment has been accomplished, you're one sign-off closer to a ticket back to civilization.
Of course, you're expected to carry out these programs with existing resources, out of your current budget. It is also true that, as Chief Station Officer, you necessarily have a certain latitude with the local accounts, certain monies from the rubium mines that are allocated to on-station operations.
And, although it is - strongly recommended - that you handle the local business with local resources, sufficient VPs are sufficiently allergic to a defeat by the competition, that any really dangerous setback can be used to effect a special, off-the-books delivery of supplemental materiel.
Old Ways Are Best!
With a game like Nexus I don't usually delve too deeply into the back-story but take the game as it is, and this one is a fast moving game of combat and expansion. That rubium is the currency of the day and that the surface you're stuck on has a number of local exotic critters that can be "recruited" to do one's bidding seemed sufficient to get the game going.
But I have been a stickler for theme coherence in other games and have been particularly critical of Manifest Destiny in this respect. So I acknowledge what you have come up with here and intend to make a copy as as a rules addendum for those who might appreciate the game a little better with a better developed theme. Nice work!