Basically the idea of what I call Legacy Mode, is that after you complete the Legacy missions, you have the options to either end the community like normal or enter what I call Legacy mode.
In this mode, both Red Talon and the Network establish a permanent enclave in what ever map you are in. These enclaves would be larger than the standard 3 member enclaves and host Venders and quest givers for their respective faction.
The Network Enclave would be more focused on helping other survivors along with giving quests that achieve that allowing you to speed up the rate of Allied Enclaves you get, and allow you to take up quests from these enclaves. I have found that when ever I want to establish some enclaves, you essentially are just playing the waiting game for them to give you a quest. This feature would allow you to hasten this process.
The Red Talon outpost on the other hand would focus on clearing out infestations and possibly Plague hearts. Missions could include freak Hunts, rescuing wayward operatives, and maybe tracking down a newly popped up plague heart. Sure you cleared out the valley of the plague, but what is to stop plague horde from entering the area and re-establishing itself? Add in new plague infestations with all the plague freaks that folks have been clamoring for. Also we could throw in some prestige rewards for those who are looking to gain the resource outside of Daybreak. (A very much requested feature.)\
The concept here is to provide a more fleshed out "End game" in which the game gives you a bit more challenge while handing the player the resources to engage in this content. It will basically take out a bit of the RNG in the quest system where you are waiting for quests to do and allow you to start them on your terms.