how about making the game replayable by adding a "Defend" game mode:
You [and a number of allied mechs] have to prevent a group of mechs [or multiple groups/waves of mechs] from destroying a specific building [or a set of buildings].
Required:
- A way to start the defend mode: main menu or command-line parameter
- Either procedural generation of a level + placement of the important-building (command center, sensor/sattelite dish, factory, pump station...) + placement of attackers and defenders or a way to create maps for that game mode
- AI needs to aim for the building but defend itself for surviving until it can reach the building
- Win/lose notification/screen
Optional:
- A method for enemy waves to enter the map: dropships for example