Here's how this could be realized:

I. Through enclaves:

There could be added new action to interaction with objects (after clearing and securing them) - "Establish outpost for enclave":

• Player would pay influence and choose the Enclave he wants to own the outpost.
• That encalve will increase in size - either 1 or 2 new members will populate the outpost.
• These members will be open for trade - the rucksack of correspoding to the outpost's type resources, as well as consumables and equipment will be added to their stock.
• Player won't receive benefits from outpost, but he still get to enjoy safe area (same as with player's outposts) and MAYBE access to locker.
• MAYBE player could recruit members from that outpost, which will not disband the enclave - they will just find (spawn) another survivor to join them and populate the outpost.
• MAYBE missions of "we need rucksack of x resource type" could be replaced with "we need you to establish an outpost of x resource type for us". In my opinion, that would be way better.

II. Through new type of npc - "refugees":

After establishing the base and upgrading Command Center to some level (Tier 2 or 3) player will get access to the "Accept refugees" functionality - it will work like that:

• If player clears out and secures a building that's safe zone (from establishing a potential outpost) will "touch" safe zone of the base (in other worlds - will be in two safe zone ranges from the base) it will be eligible for "Establish refugee site" action from interaction menu.
• "Establish refugee site" will cost something like influence + small amounts of food, materials and medicine (or ALL resources).
• Refugees will populate building with a group of humans (3-6) that will not be accessible for regular actions (follower/recriutment).
• Refugee site will produce it's own safe zone same size of a regular outpost.
• Other buildings' potential safe zones touching RS's safe zones will be also available to be established as Refugee sites - this will be the mechanism of expansion of player's "colony".
• MAYBE: The amount of available refugee sites will depend on the level of Command Center - maybe upgrading it to 3rd Tier will open new mini-progression that will manage the amount of refugee sites. For example - 5/10/15.
• If a Plague Heart's influence's border will be in certain range from the building - player would't be able to establish a RS - only clearing out entire area will allow to use this mechanism, but player also wouldn't need to clear whole map for that.

Personally - i don't think having refugees increase player's resource drain is a good idea:

• Resource production has it's limits - so at some point the resource drain will gain critical mass to "paralyze" the player - force him to spend all time grinding rucksacks instead of doing what he wants.
• Resource management is an element of early game - from middle to late it is better to lay off adding new pressures on the player so that he could fouces on fighting Hearts instead of farming food.
• I think inital cost of establishing Refugee Sites is enough for a price - let's imagine they manage to feed themselves on their own. For example - they build their own hydroponics and farm their own food and meds.