I was working on a Helios mission thingy myself but I accidently overpowered the vessel a little.
For the missions you suggest, I'd say they all hold their own fun elements.
A possible suggestion for a mission:
4) 8 player coop: an Ubuntu council-member was on his way to rally Gef's in an effort to make a strong stand against the Tev's. Unfortunately, the captain of the frigate the Ubuntu member is on has different intentions and believes he does the right thing by delivering the VIP to the Tev's to end the war one way or another (believing the council-member has enough information to undermine the UEF defences, forcing a surrender and little-loss-of-life solution). It's up to a squad of Lao Tze to disable and then recapture the frigate before the Tev's can get away with the VIP. The VIP must then be escorted to a jump gate which ultimately is blockaded.
- Disable the Frigate.
- Hold off increasingly strong Tev reinforcements (from fighters and a cruiser, building up to the Atreus herself mixing in the fight). They use tactical weapons (stiletto's, trebuchets) to try and disable or disarm the frigate.
- A constant, high-presure demand of performance: the players must quickly switch from escorting to de-beaming, back to escorting, etc.
- The players can try and get the frigate out of there in one piece for a bonus condition, ultimately though if the frigate is too damaged a transport is launched which remains the primary objective (having to be escorted to a jump gate).
- The players must resolve the blockade, either by damage the destroyer (Atreus) which then falls back or creating sufficient of a distraction in some way (depending on met conditions).
5) The players are part of a highly trained GTVA dead-squad and must sanitize a supply base, with intent of catching the bigger fish (possibly a Solaris or a wing of frigates) by surprise on their return. A UEF medical vessel will serve as bait, which can be spared or destroyed (a secondary objective may indicate sparing some witnesses to spread news of terror). Sparing the vessel gives the player a completed bonus objective: propaganda (leaving witnesses to tell of the great defeat will inspire fear into the Sol citizens), but will also result into more reinforcements coming to the medical vessel's aid, making the battle more difficult.
- The player is launched from a GTVA destroyer.
- Destroy containers, docked supply ships and a small installation.
- Take care of a fighter complement and a Sanctus cruiser.
- Disable the medical vessel, but spare it's comm. Extra reinforcements will come to it's aid, until it repairs it's engines and makes an almost instant crash jump for UEF territory.
- Alternately destroy the medical vessel too, at the cost of not getting extra enemy reinforcements to fight and not completing a bonus or secondary objective.
- When the returning capital ships (frigates or a Solaris) return, the player has to quickly disarm the ships to prevent their destroyer being devastated (the GTVA destroyer draws away the firepower from the UEF ships, but has it's forward beam cannons destroyed on a first strike).
- The players emerge victorious when the UEF ships are destroyed, or fails if the destroyer bites the dust.