May I give some golden advices?
I player Armada2 for many many years, and Freespace2 aswell. In Armada2 you attacked your enemies with 200+ ships while in Freespace2 you never saw more then 1 Orion, 1 Deimos and 6 squads of fighters in a battle.
My advice:
-Make shipbuilding very slow. 3 minutes for a deimos, 6 minutes for an Orion and so on. People who played the Starwars mod and who wait 20 mins for a Super Stardestroyer to finish know what I mean.
-Allow a limited number of crew to be used. Would be unrealistic to build 20 Orions. Give enough crew for 4-5 at most maybe.
-Make ship speed low, at this way you got enough time to send fast fighters in to try and intercept the enemy.
-Make fighters function in squads (not solo fighters) as is done in the B5 and SW mods for Armada2. This gives a more overseeable situation.
-Make nebula's harvestable, this could result into a more freespace enviroment.
-Allow upgrades of weapons. Fighter Subach -> Prometheus etc.
-Armada2 has the ability to fuse ships. (Borg cubes and galaxy-class seperation). Use this! Allow 3 squads of the same fighter-type to fuse into one squadron to have a slight advantage.
-Armada2 has wormholes, Freespace2 has Jump Nodes. It could be wise to make Jump Nodes in the game, acting as the wormholes.
-What if you make a messon bomb and allow freighters to fuse with them into a freighter hauling a messon bomb? (Like making a Galaxy class saucer section fuse with the stardrive section). You could then unfuse where you wish to leave the bomb and click detonate to create a large explosion. If you could make an AWACS class of ship it could cloak the bomb and itself, resulting into an unlucky Orion flying by, being blown to bits. Tactics are what the GTVA is well known for.
-At all costs, avoid the situation of: build that type of ship to win easilily. The starwars mod allowed 100 fighters to be build per minute. The players simply builded fighters-only or fighters + light cruisers to quickly overwhelm the enemy, leaving tactics to nearly 0. Freespace is known for: pop up behind the planet and kill the Ravana or hide in the nebula and ambush them with a scisor formation.
I've modded (mainly 3d modeling and texturing) since my 13th and I know some amazing things can be done in Armada2. Try to exploit these things to the max.