Okay, here's one: in the tumult of battle, Omni's lines surge forward, and Andy and the small forward base he's commanding suddenly find themselves deep within enemy territory. The mission begins with Andy's last transmission into the void as Omni's jamming satellites come into range. Something dramatic, like "Take care of Jana for me...."
The mission is a siege/survival mission, with Omni trying a different tactic with each wave of attacks. The idea is to create twenty or thirty unit groups, their unit compsition each finely tuned to a specific strategy. You could have an all-cyclops unit group, a commando unit group made of about five to ten Fox's, a mix of six hydras, two liberators and two cyclopes, etc. You get the idea. Basically, build the base, man it with troops, and put yourself in Omni's position: decide how you would attack that base, and create unit groups and corresponding triggers/areas that reflect your thinking.
Here's the catch: they all need to be RANDOM unit groups (with the random unit group box checked) that spawn at specific areas at the edge of the map. Make the following trigger:
Conditions:
Every 180 seconds
Actions:
Create Random Unit Group
You could challenge the player in different ways:
Limit the galaxite. It's a seige, right? The player should be sparing on resources. If you go this route, make sure to keep the attacking unit groups on the small side.
Use drop ships/stealthy infiltration. Have corporate raiders drop inside the defenses, to take over galaxite facilities or something. Commandos can sneak in (spawned in hidden areas) to destroy bullpups.
You could send dis-information in the form of ecoms - they should be obviously false, like for example a small ecom from Omni security that reads something like: "Andy, my boy, this is Olstrom. Acme wants you to surrender. When the next wave of commandos arrive, let them through." and follow such a communication up with a commando unit group (not random, this time) that is to move in to kill Andy. Use this tactic sparingly if you want to fool the player, or use it liberally if you want to create a little drama.
---Finally, don't make this a survival mission, with unending waves of Omni attackers just to see who can survive the longest (but everyone eventually dies) - I find those annoying. Provide the player with an end. Possibly it's reinforcements, or maybe a previously secret way out.
If you're in the mood, you could do multiple levels, one where Andy and his troops sneak out through heavily defended lines, and possibly a third where Andy gets back to Acme territory and launches a massive counter attack to retake the base, possibly even using the original map.
Have fun!
