Once we have NPCs, we can have proper succession games, where when you die you can take over as another NPC in your camp.
This allows for waaaay more endgame content, depending on how well the NPC AI is coded. There are other games where large numbers of NPCs can be managed in colony-mode, although that may be beyond the scope of Zomboid. I'm thinking Dwarf Fortress and Rimworld here, but this creates a lot of extra layers of NPC behavior and management beyond what would be required for "collect survivors into a camp", which that one mod does for Zomboid.
My hope is TIS would go that route, of course, and implement at least a skeletal structure for more colony management, effectively creating a second game within the first. Then you get the joy of building up your own colony, plus diplomacy/fights with other colonies, mergers, attracting immigrants and refugee groups, and generally rebuilding society from scratch, all while fending off zombie hordes. Also there's intra-colony factional struggles to manage. Say you die, you take over as your next-in-command, but maybe they don't have the same influence in the colony and end up being subjugated to an AI-led colony, where the RNG personal characteristics of a new leader take it in a whole new direction, and you have to work to build up your own faction and influence to take over again. You can go so many ways with this it's crazy. Get all CKII up in it.
I'd call it Rimzoid, but that's why I'm not in advertising.
They could always release it as DLC/expansion, I'd buy the s--- out of that to support them for the added features. My hope would be that TIS would split off into "next game" staff and "add lots of new AI/NPC stuff via DLC to Zomboid" staff. Steady income stream for a couple coders. I mean, we, the fanbase, are pretty used to waiting a long time for content now, so no rush. I'll wait a few years and buy a "colony simulator" expansion to Zomboid no probs.
One thing that I have noticed myself is that having more zeds nearby increases load on the server.
Example: this graph is a load on the host for 1 player roaming around a base with some zeds, just your normal play on foot up till halfway. Then 2 helicopters happened, and player hides in a base with ~150 zeds going for him.
As you can see, that's about x2 load you get for additional 130-150 zeds at once nearby.
You can try to up your server hardware (mostly CPU) several times and see if that helps it.
Tried those settings. Looks like we are still having issues. This didn't ever happen before we increased the zombie population but unfortunately we all prefer the settings stay as difficult. Are there other things in the world I can remove or lower to help the server?
First of all, i agree with your "there needs to be more to do after the initial scavenge-and-fortify phase of gameplay" statement. Because it's just true. Nowadays, after you pass that step, you basically have nothing to do ; exploration is pointless. Such a pity for a so huge map...
"One, your time put into your character has to mean something. You don't just wanna be another schmuck trying his best to live out the apocalypse, you wanna have a legacy to leave behind, to actually have made a difference in the hellish wasteland your world has become, like Rick Grimes or the Vault Dweller." Seems you want to be a hero or something in a game where you are just that : another schmuck trying his best to live out the apocalypse. I think the mood of PZ stated in introduction is"There's no hope", as in pretty true real zeds apocalypses settings, not like emoteen or residentevilesque action bullshit of the Genre nowadays.
I'm pretty sure NPC won't alleviate the "no-end-game" feeling (but we'll have to "wait & see" for the release to be sure). On the bright side, they will certainly postpone it by offering an interesting way and probably add some more "in-deep" feelings : but create/manage a community of survivors is just a variant in making your own solo base imo.
About the Quest thing, 7D2D (to stay in zombie game genre) tries something like that, but it feels very/horribly like MMORPGesque repeatable quests (settled in a Zed apcalypse). The new "Dungeons" POI feels more appealing in term of temprorary/short-term objective : plus, you don't need some freaksih NPC told/ask you to go there to do something ; you can just go it by yourself, explore and create your own story. You've mentionned FO3. Imo, a "side-quests" system tied to some places (like the Tree-mutant in the north, the Dunwich mansion, all about Tenpenny tower, etc.) with their own stories and feelings seems more indicated for PZ, than an overall plot. You don't need NPC for that ; but you need some storytelling tied to the place and (probably) some scripts and such to create a "local event". Then, you have new reasons to go here & there. Storytelling is probably one of the reason why MP servers with active managements & events stuffs works well (beside the various level of "challenge" they offer)...
To completely avoid the "no-end feeling", the game need an actual end (plot, scenario, victory or deadline condition, you name it) : thks Cpt Obvious... Well, in a Zed Apocalypse, what could it be ? Find a cure (a big NO for TiS Team...) ; survive till the zeds themselves disappears (at some point, they'll decay to skeleton bones states... So why not ?) ; find a way out of the containment zone (according to TV/radio emissions, the Knox Event become pandemic, so, it's not really a good ending, but well...) ; wait until some team from out of containment zone come to rescue you (the chopper didn't agree at all)...
I don't think the TiS team want to implement any of that (doesn't see/read anything like that since 2014 ; maybe i'm wrong). So, i guess we have to live with it and consider the "boredom in the end" is just another way for PZ to tell you "how you died".