For Mom.

To capture the flag, the flag carrier could need both flags... or
To capture the flag, the flag carrier docks with their team's trident... or
To capture the flag, the flag carrier have to enter a designated zone on the opposite end of the field.

To defend the flag, defenders could need to shoot attackers more than once... or
To defend the flag, defenders could place defense turrets... or
To defend the flag, defenders could use npcs.

And, that's all I have for now, tell us when you want more bug testing, we'll either break it in or just break it.

Flag carriers should be marked somehow. A glowing ship or just a different color on the radar.

Put trophies into the player's inventory at their home station.
Most light fighters don't have a lot of cargo space, so two tag outs and you're full. You have to leave the game in order to dock and stash your worthless scrap metal!

Only allow captures while your team's flag is secure.
Kind of like how it works in Unreal Tournament. Make it so you can only score a capture if your flag is floating in your team's space or held by one of your team members. That means you'll have to go after the enemy to get your flag back if you want to win.