I think embracing the notion of territorial conquest being an ingrained point of the game helps.
Yes space battle is a grand ole time, it is also the prelude to actually getting control of the territory in question.
Capturing Prize ships is cool enough, as Ram brings the concept up in his angle/desires. When it comes to Opposing
Facils, I go back to a thought I raised earlier today..
Capture the Flag. The planet is the flag, only ground units can capture the flag. The goal is to get your troops through to the ground and fight and win there. This in no way takes away from our glamorous space combat, in fact if you ask me, it makes it more strategic and tactical because you're not just trying to destroy opposing ships- you're trying to keep them from getting landing craft/troops/gavs to the planet.
So just have a blurp in regulation about the ground game.
The name of the game is capturing planets. When your troops have eliminated all enemy units and facilities on a planet, victory is yours. The space battle is immediately truncated, all opposing ships automatically withdraw to a friendly planet. (this eliminates the common practice of Fight to the Death when it comes to capships, now your capship value is not only in its combat strength alone, but it's ability to land troops and support that endeavor)
When victory is achieved, the winning player who now 'owns' the relative planet gets 1 free facil to restablish there (as long as there was at least 1 opposing facil there you took out). No more no less.
I like it myself for reasons listed above as well as increased structure/order.
Along this line you could go further and create different Battle Types or Objectives. So you get to a planet to begin your attack, is it a "Raid" or is it an "Invasion" ? If an Invasion, then the above dynamics could apply for ground combat. If it is a Raid, then that regulation is ignored and just business as regular. You could turn it in to an Invasion de jure and win sure, but you don't get the benefit of the Truncated Space Battle as would be the case when you won the ground if you had declared your operation as an Invasion in the first place.
So you got your choice, is your attack a Raid or an Invasion? Invasion regulation would put the most weighted value on the ground battle outcome. Raid regulation would put the most weighted value on the space battle (i.e. maybe you're trying to kill a platform or just capture some ships for fun, maybe a successful Raid operation gives you some kind of currency/value)