Boss battle to unlock GenMat
I'm pretty sure this will never be implemented but let's just discuss this for fun.
I remember back then playing a similar game to MyM called The Mighty Quest for Epic Loot there was a mechanic that in order to get to the treasure room you had to defeat a boss.
Now imagine this. Devs could create a few bosses to choose from. Those could be various mutants with different sizes (1x1x1, 2x1x2, 2x2x2), different types of attacks and different health pool (between 6-10 hits to kill or double that for co-op raids). The GenMat would be sealed as long as boss is alive. Each outpost can have only 1 boss that needs to be placed near the GenMat and let's say the boss can't go further than 7 block distance from the GenMat.
Of course this being an FPS with fast movement and full 3D building creativity makes this idea way more difficult to implement than in TMQfEL but I can imagine this could be fun xD