I think the concept sounds fine, having a space map does not necessarily mean that it will have to be empty. In the event that you add collision for asteroids, asteroid fields will provide natural obstractles which have to be cleared up before you can pass them with capital ships. Just be wary that depending on how you check collision, having too many asteroids could be heavy on performance. As for other space doodads, i can probably provide some, if you have something particular in mind. The way i usually make my space maps is that i use alpha tile for the ground, and then just use either a space skybox, or some different doodads which i have "sunk" through the ground to make them appear beneath the ships. It can provide some pretty cool effects. Perhaps the planet you are fighting over can be seen in the distant, underneath the battlefield?
As for gameplay, these are my advice:
- Have a map that is symmetrical in the existence of bases and objectives. Three stations per team would make it easy to keep track of a teams progress, by seeing how many stations you've killed. It could look nice to have a diagonal battlefield.
- If you are to have both RTS and TPS elements, make sure that the RTS is not too micro intensive, and that it can be left unattended for some periods without losing you the game. Basically, you could narrow it down to placing target points for individual squadrons, and have them manage the fighting themselves through AI. Perhaps the largest ships would spawn fighters, to add some strategic importance.
- Use hyperspace sparsely. Perhaps have it as a special ability wich you can unlock through points, or give it a long cooldown and only allow capital ships to use it. Having too many units hyperspacing around will be confusing and frustrating for players.
- Make sure the gameplay is very goal oriented, but also somewhat casual. If every player needs to have a lot of background knowledge, or do things in a very specific way, the game will not be very fun for new players. One of the issues i noticed with Battle for Tatooine was, that whenever you went off to do side missions (which weren't very fun), you would lose too much ground in the battle to win the game.
Anyway, the campaign is also not locked, so you can disable the music or whatever as needed.