Ive played the game quite a large amount of time now, and greatly enjoy it.
What you have is a battle engine, but not quite yet a game. I like the hands off approach to the combat and love the puzzle like quality of arranging and placing orders for the troops.
I only have one large suggestion;
There are currently two primary parts of the game (fleet deployment screen and battle screen) .
I see no real reason why they are kept isolated from each other.
Based on some kind of time (or other) condition extra ‘waves’ could be triggered for both sides of the battle.
By having backup forces joining the battle in an integrated fleet deployment and battle screen, choice (which is the key to all good games) could be made in real time.
Many thanks for the hours of fun thus far from your game, and can not wait to see how it progresses.
-Knytemare
Good suggestions in your post. I’m half of a father-and-son GSB duo, and my kid has been asking me increasingly pointed questions about if the game will eventually have reinforcements. Of course I have no clue, and I tell him so, but now we’re studying the subject in detail W.R.T. game balance. I happen to like the notion of staggered deployments; not Survival mode, mind you; just a small group of fresh, unscarred units to gallop over the hill and try to pull one’s metaphoric chestnuts out of the fire. 
I think that a late-arriving combat group should by no means constitute an absolute guarantee that if you were losing badly, thou shalt now win handily. It should extend your chances of such without automatically being a deus ex machina. For smaller battles, perhaps a single fighter squadron or a trio of frigates. For larger battles, perhaps a pair of light cruisers led by a heavy cruiser, with a couple of fighter squads (one for escort, one for anti-ship assault). I concede that’s a tricky road ahead to add suspense and fun while not wrecking game balance utterly. But hey, that’s why we debate these points on cliffski’s nice forum here.
If you could specify the exact composition of your reinforcing group but have it stuck on a variable timer where all you can do is choose the minimum interval prior to which they cannot show up, that also could be fun. I like the semi-random nature of that. Or perhaps the opposite - pick exactly how many minutes & seconds until reinforcements show up, but their onboard mix of modules is randomized by the game program.
Again, if this is ever implemented, it has to be sufficiently different from Survival mode to still be enjoyable on its own merits.
This is a very interesting insight. It would make a certain degree of sense to simply deploy directly on the battle screen.
This would be an interesting direction for survival mode to grow into. Rather than just fighting until you died, your surviving ships could be repaired and reinforced (to varying degrees) in between the waves. By specifying different amounts of resources available in each reinforcement (and the sizes of the enemy forces), you could achieve many different scenarios: A battle group’s campaign experience (e.g. Company of Heroes, the Lost Fleet series), a single long battle (Verdun, Stalingrad), or who knows what else.