They're a mobile FARP for up to a squadron of ASF, and could refuel any accompanying Small Craft at the same time. Basically, they're your "bases between bases"... :)
The intuition of the in-between base doesn't work well in space because the fuel & time required multiplies. For example, if you have point A and point C with point B in the middle, then dong A->B->C requires sqrt(2) more time as long as the fill up at point B takes zero time.
The other tricky thing about this is that it creates a target. This leads to the question: do you defend it? If you defend it, that requires significant resources (see the EDFs). You could avoid by using secrecy (which the battlesats do), but that's somewhat risky, and this one now has more at risk.
The use cases include but are not limited to
- all the things the battlesats do except shoot their NL
- provide a convenient landing pad for fighters to refuel/rearm for example
- Ammon squadron 7 have fired off all their external ordinance in a protracted dogfight rather than spending 2 hours returning to base they quickly set down at a lily pad, re-arm and re-engage faster.
- Sending your dirtside heavy fighters to engage away from planet.thwy are able to lift more easily without external ordinance and arm up at the orbital lilypad.
- SAR and emergency platform, for example to recover fighters that were in operable following an HSE
- providing a platform away from strategic targtes, for example to detain a suspicious drop ship that's suspected of carrying nukes.
The point of the battlesats is "eyes on the sky". It's modestly better than the battlesat (cheaper, with a better secondary mission), but still nowhere near as good as those Skywatch satellites which are an order of magnitude cheaper, require zero crew, and have super-elite detection checks. Given that, it seems we should satisfy the primary mission with the Skywatch satellites and then consider whether or not secondary missions can be promoted to primary.
W.r.t. Refuel/Rearm, there's some point to this. There would be much more point if we were using the Rievers in the PDF, since they can't reach space with a full bomb load. The Ammon's are merely reduced to a 3/5 with full hardpoints and the Chaeronea's are reduced to 10/15. The fuel cost of reaching orbit is not
to significant (fraction of a ton) although obviously topping off could be helpful. Overall, it seems like a modest value? Alternatively, you could base out of something like this to reduce exo-atmospheric reaction times, which may be a greater value than topping up fuel.
SAR: Smallcraft are better and comparably priced.
Emergency platform: You probably need a tug to handle this first, and on moons or near civilian stations that's probably all you need. Can a tug be made which can grapple a damaged ASF and land on a planet? ... it looks like "yes"---you can make a 3/5 200 ton smallcraft which can dock with a damaged ASF and carry the ASF through the atmosphere to a planetary base. This would take longer than carrying it to satellite, but you would gain the protection of the atmosphere.
Detaining platform: This is useful, but typically not a military function. Leaving customs stuff to the law enforcement budget seems reasonable as it leaves the military with a clearer mission: break stuff as necessary to protect the system.
Overall, it seems like the refuel/rearm choice is the most plausible. It's not clear this is the right scale there though. There are _many_ planetary ASF, so handling 6 is pretty piecemeal, and the startup cost on a station is pretty substantial. It looks you can double the price and handle about 5x as many ASF/smallcraft with a somewhat larger station. That's a more appreciable fraction of the planetary ASF. A significant difficulty with the adding the station near a planet is that it becomes a valid HSE target. As long as it's kept low cost/value that's probably ok, but it's something to keep in mind.