money = variable
Make a key for showing the money on the screen with a training message.
Make a key for putting yourself in buy mode, then if it is pushed again, you are out of buy mode.
In buy mode, you should be able to push a whole bunch of keys, which are shown on screen in a message with the key, what it buys, and the cost; also using the training message thing.
I suggest making the prices similar to the kill values, only more pricey.
Also, edit the tables so that you have a light, normal, and heavy variant of each fighter/bomber. The light variant has less powerful weaponry than the normal, and the heavy with more powerful weaponry than the normal. The normal variant is the stock ship.
Also, everyone should start with an ultra-light Ulysses. Means: Ulysses with slightly compromised health/shields and the weakest weapons. No secondary weapon for this. This encourages the players to at least get the light version that has the full heath and a secondary weapon.
SUGGESTIONS:
When a fighter is killed give 1 money.
When a bomber is killed give 2 money.
When a non-fighting ship (transport, AWACS, ect) is killed give 5 money.
When an Arcadia is killed give 25 money, and a Ganeymede 20.
Cruisers; Fenris = 6, Leviathan = 10, Aeolus = 15, Aten = 5, Mentu = 9, Cain = 10, Rakshasa = 15, Lilith = 20.
Corvettes; Deimos = 40, Sobek = 35, Moloch = 30.
Destroyers; Hecate = 70, Orion = 80, Typhon = 65, Hatshepsut = 75, Demon = 85, Ravana = 90.
Anything higher is overkill.
Bases are very powerful, like the HP of a supercap.
Also, for every kill you make, you get a special form of money called "personal money" that lets you buy craft for yourself. You get 1 for fighters/bombers, 2 for nonfighters, 5 for stations, 4 for cruisers, 8 for corvettes, and 15 for destroyers. Depending on the strength of the craft you wish to get, you need to pay money for it. Terran/Vasudan fighters are generally 3-10 money, while bombers are 6-20. Shivan fighters are 5-15 money, and bombers 10-30. Everything Shivan is more expensive.
If I was to do anything after my Capship campaign, THIS WOULD BE IT!
Edit: Perhaps the cost for going to a new ship should be reduced by half the price you paid for the ship you have. IE, if you are in a light herc (say 5 money) and want a heavy herc (8 money), you will pay 5 credits for the heavy version. Also, if you die, degrade your ship. IE if you die while in a heavy Herc, you are respawned in a normal Herc. Mabey if you cant get degraded you should lose a couple credits.