I have recently been replaying the FS2 campaign, and I feel it could be improved. Having played some TIE Fighter as well, I noticed that the Freespace 2 campaign is rather lacking at times when it comes to Bonus objectives. Here is a summary of what I believe we should change or expand.
CAMPAIGN CHANGES
One: Include AI & SCP improvements, such as AI using Trebuchets appropriately.
Two: Add more opportunities for the player to make a difference in the campaign, such as ships surviving a battle and appearing later on, getting different loadouts if conveys are destroyed/saved, and so on. Stuff like what was done with the mission about damaging the Sathanas is really cool in my opinion.
Three: Make some battles larger in scale if appropriate, since the engine can support more stuff.
Four: Additional cinematic flair where possible.
Five: Rebalancing to be more canonical and to take AI changes into account.
ex: Correction of the Mjolnir to have missiles, like in the briefing, AI pilots using Trebuchets, Colossus having all turrets. (I hear that it is missing some.), improve the Artemis D.H, Tag-C, Artemis Overclock, Nahema underclock, Bakha overclock, Mentu beams, Check-Hull flags for turrets, Bahka-Helios secondaries, ect.
Six: Restoration of content & ideas that Volition didn't finish, such as Colossus and the waypoints in High Noon IIRC.
MISSION CHANGES
Surrender, Belsaurius!
An extra dose of cinema would be good. Placing the Psamtik and Belisaurius further away from the player's location and having them exchange broadsides should be good at demonstrating beams. The only problem is the boredom factor for veterans, and that getting between the two ships is a good lesson to rookies about the dangers of being in the crossfire. Perhaps a little bit of of show and tell would be good. A small ship or fighter from the GTVA could get caught in a second exchange of firepower, getting destroyed while screaming an appropriate epitaph. After the Belisaurius gets blown away, an NTF Fenris can come onto the scene, so the player can get involved and learn about close encounters with beams with minimal danger, with the Fenris using the Slashing Beam once on the player.
Place of Chariots
My opinion here is more along the lines of what I perceive to be a more realistic approach to the containers. That is, I think that Command would be interested in checking out the contents of the containers since they might have information, supplies, and so on. The fact that they are shielded ought to be a big clue about their importance. Perhaps a NTF Fenris with some fighters could warp in to destroy or protect the containers. Maybe the Iceni could be scanned as an bonus objective, too. (Since it is carrying ETAK)
Lion at the Door
Preservation and scanning of the Shivan cargo would be a good bonus objective, I think. It is likely that Command would be interested in knowing how Shivan technology and methodology has changed, and nothing is better for that than looking at their supplies.
Mystery of the Trinity
While I don't mind surprises, it seems odd to me that the Trinity is destroyed so easily and without a chance to ensure the survival of the ships you are supposed to protect. I think adding a Secondary objective of protecting the Discovery would be good, and having the actual repair and survival of the Trinity to be a good Bonus objective. In short:
1) Survival & Escape of the "Discovery" as an Secondary Objective.
2) Repair & Escape of Trinity as an Bonus Objective.
3) Rebalanced enemy fighter waves, if Trinity becomes an Bonus Objective.
4) It would be nice to have some sort of reward for Trinity surviving. Maybe an extra SOC mission later on?
The Great Hunt
An fairly good mission already, but I think it could use some bonus objectives.
1) Scan the Ravana as an Bonus Objective, which makes the Ravana 10% damaged in the next mission?
2) Make it possible for both corvettes to survive, with them appearing in "Slaying the Ravana", as a nifty bonus for the player. They ought to retain some damage to reflect the battle in progress.