There are several problems with the campaign game from a design standpoint. It is not technically a campaign game but rather a reverse survival game. Rather than in a survival game, where at first you are strong and over time they wear you down, in this game you start out extremely weak and grow your fleet with expanding economic strength, assuming you don’t take too many losses.
That assumption however is a rather far fetched one, in that you are not up against equally matched starting forces of AI empires, but rather other player’s fleets from roughly equivalent turn counts (or so I surmise). This is fine on the surface as a battle generator, even cool, except for the problem that while you have to defend many fronts, you will certainly after a few battles find yourself up against another players main offensive fleet, whereupon you are almost certain to take serious losses, even assuming you win.
This would be fine if your opponent were thusly also weakened, allowing you time to build up. Alas, this is not so. Your every front is still under potential assault by other player’s main assault fleets that have been fortunate enough to ‘not’ be so weakened. It is thus a certainty that if you ever fight a battle in which you take significant losses to your primary offensive fleet, the game for you is lost. You would be well advised to start over.
I play campaign games almost exclusively. The battle game is useful for me only for testing new designs and races, and gaining honor to unlock stuff with. The only campaign game I have ever played to victory however has been with a mod race that I have figured out how to use to great effect (Union). Even with that race however, I have on occasion encountered extraordinarily well designed (and large) fleets that have inflicted massive losses. Inevitably that means start over.
GSB has a great combat and design system and the graphic space battles are great fun. If this were a true 3X space campaign game, this would quickly go down as one of the greats along side many big publisher titles. Unfortunately the campaign game is ‘not’ a true 3X game, not by a long shot. I understand that this is a pretty much a one man show, and it is a marvelous achievement given that. It is also very understandable that one person not be able to handle on their own a full fledged 3X campaign game.
I dare say however that the modder community, small as it may be here, would be more than willing and able to do much of the brain and grunt work in turning the current game into GSB 2.0, the 3X game. All that would be necessary is the coding to permit the building of planetary facilities, interfacing with a research screen, the creation of general purpose (modder scriptable) external variables, and code to permit others to script AI behavior (the last is a killer, I admit). Modders could take it from there.