I think adding a "Full" module would take more play testing than most contributors have time for, but I wouldn't be surprised if people created additional modules that could only go in one of the three slots.
Concept as it is now: Timer countdown (Atlantis sinking) 1)start with placing 1 hex in the middle, 4 cities connecting to it and then fill in 2 rings of hexes around the cities. Every player places 4 meeples one on each city. You need to get them off the island while there's still room. For every meeple that successfully leaves, you get 1 point for it and every earlier survivor. (Including opponents meeples)
2) on your turn discard a hex, one of your player pieces or one of your resources permanently to the gamebox. You get 1€ for every type of terrain/piece of the same color/resource of the same type that's already there. Game ends if no more of a certain thing can be discarded.
3)on a players turn they must move a hex from the board OR one of their units OR one of their resource cards to the gamebox. This piece is no longer in play. Once the board is down to 4 hexes or a player has lost all units, the game is over. (It can end earlier due to other modules)
Obviously it would need playtesting and made to match actual rules. Assuming I'm still interested once I buy 504, I might even flesh it out peoperly and post it.
I'm just saying, with the framework that Friese has made in place, it is not outside the realms of possibility that we're flooded with modules.