Lady Liberty Prime.
Somewhere down the line, we gotta have a giant mech walking on planets. Could come from the DSS, and have a whole arc to both finding the schematic and the building process of the giant mech.
Could have salvage missions where we collect wrecks of both recent and old war mechs as the beginning process of making the first Lady Liberty Prime. A mission that has no time limit, but requires a set quota of collected salvage. Players can salvage mechs to reach victory quota, but can continue salvaging more mechs to further progression of creating Lady Liberty Prime.
Then maybe a MO or two based around collecting samples and the collection of High Value Assets from the Automatons. Which means the requirement of going onto D10 difficulty to collect the bot heads from the fortresses. Wouldn't require many for High Value Assets, but can still prove difficult to accomplish.
Have all the above as the first half of the creation process of the giant mech, then the next half can lead to the defense of potential pilots for the mech.
The next half will include the defense on a planet where the first Lady Liberty Prime is being built. Faltering will lead to a long time delay, and a potential new mob on bot front.
If the Helldivers won, then the first Lady Liberty Prime deployment will happen, and then the next one will be in production later in the future.
DSS can have another page for Lady Liberty Prime construction, and where the DSS is currently, AND with enough votes too- the DSS will deploy the next fully built Super Mech.