There is a general consensus that diplomacy in PP is currently lacking, and the devs themselves are unhappy with how it turned out and want to do something about it (see the last Q&A).
At the same time, there are many complaints about how uninteresting base management is, and how additional bases hardly add anything to the gameplay.
My proposal is to address both issues by reworking diplomacy, using foundations and mechanics already in the game, and without adding (hardly any) micromanagement.
So regarding diplomacy, I suggest that:
1) PP have the option to declare a haven to be under its protection and from then on get a % of the resources generated there, the kind of resources depending on the districts - including raw, classless recruits that can be trained by PP into any of the classes it has researched - and the % depending on PP’s reputation with the haven's leader.
If the haven gets attacked, whether by Panda or another faction, and PP doesn’t respond, the Haven doesn’t get immediately destroyed - rather one of its districts gets damaged and PP suffers a big reputation loss with the Haven’s leader and a smaller reputation loss with the leaders of nearby Havens. Repeated attacks will get a haven destroyed, causing a massive damage to PP reputation.
In addition to resources, depending on the reputation level reached with the haven’s leader, the Haven can provide equipment (allowing to get their factions technology through reverse engineering), or trained recruits (replacing the current recruiting system).
2) PP’s reputation with leaders of the various havens be largely independent of the diplomacy rating with the factions. In fact, havens should attempt to break away from their factions and become independent (a special tactical mission to accomplish the coup becoming available to the player), if the leader of a haven and the faction to which it belongs have very different opinions about PP. For example, the leader hates PP because it has raided it in the past, but the faction is allied to PP. Or viceversa, PP has protected the haven time and again, but the faction is at war with PP.
3) A higher diplomacy rating with the faction will mean that the havens of the faction will also send resources to PP, as in the case of the protection agreements, but a much smaller %. This is basically the faction ordering the havens to pay a tithe to PP to encourage the alignment of their interests. Also, and as is now, higher diplomacy rating will allow to share research, but it should be reviewed to be a bit more restrictive.
4) Becoming allies with one faction will automatically lower the diplomacy rating with the other two factions to neutral, but repelling attacks from a faction on a haven will not lower the rating with it. The end missions for each faction should be available regardless of diplomatic status with the faction. So you can be at war with Synedrion, but still get their ending.
The purpose of this system is to give the player a greater agency in shaping PP's role and making it more distinct during the whole game, not just at the end: is PP only concerned about fighting the Panda at any cost? Or is it also protecting humanity from itself, trying to keep a balance between the factions until some choice has to be made? Or does it wholeheartedly embrace the ideals of one of the factions?
At the same time it would make use of elements already present in the game (districts, havens leaders), address the complaints about recruiting, provide a less tedious and more logical way of acquiring resources than trading them for food, etc.
This changes to diplomacy mechanics would be connected to PP base management in the following manner:
1) There would be a new building: an aerial cargo dock and warehouse facility to receive resources from havens within a certain range. It's a special building because it is built above the ground. More on that in 2).
2) All PP bases would have the option to be sealed, which will make all their facilities under the ground invulnerable to attack but inoperative until reopened (requiring a team to be sent there). The facilities above the ground will be destroyed if the base is attacked and there are no soldiers to defend it.
3) The PP bases that serve as receiving hubs of resources from havens will get visual cues re what is happening there, i.e. so you can see the drones with the stuff flying in and out, some civilians sorting out the cargo, etc. and possibly some special building options to enhance their roles. This could also tie into some managerial perk for PP soldiers, as suggested in this ticket https://phoenixpoint.canny.io/feedback/p/base-personnel-perks-for-soldiers.
For example, a PP operative with the "diplomat" perk would increase the reputation with the havens leaders over time, a "logistics expert" - the amount of resources received, a "teacher" would train raw recruits faster into classes, a "scientist" would give a boost to lab output in a "hub" base, and an "engineer" to factory output, just as possible examples.
These are the basics - I think it’s easy to see how the system can be made much more complex and have a larger, or smaller degree of abstraction VS micromanagement.
In any case, even at the most abstract level with these changes PP bases will have much more character: some bases will become hubs, that are critical for obtaining resources from the havens. They will require protection. However, not every base can be protected, so the player will have to make a choice which bases to make into hubs, based on the havens around it, what they produce and the faction to which they belong.