Towards Sandbox Pathfinder

I love Pathfinder 2e, but the thing that I like least about it is how strongly the rules lend themselves to linear play. You get XP for fighting, so you're incentivized to find and beat every encounter possible. The connection between level and balance means that if the players take on a threat too early or too late it will either immediately kill them or be a boring cakewalk, so the GM is incentivized to design encounters around the level the characters will actually be. Unfortunately, when it comes to published modules, this often means that the GM decides

My ideal of game design is the Alexandrian Remix of Dragon Heist. It has interesting factions of all sizes with realistic motivations, awesome bad guys and locations, and tons of tools for the GM to work with including both tons of interconnected locations, props/handouts that the players can find to help gather information, and response teams for when the villains take a more active approach. I have run this adventure twice now, once in 5e (for which it is designed, though I redid most of the monsters) and once in Pathfinder 2e (with proficiency without level). I might clean up and publish that conversion at some point if I have time and there's enough interest.

The same question has rattled around in my mind - how do we make an adventure (or adventure path) as free and open as that Remix using Pathfinder 2e? Especially adding level to proficiency?

The Pitch

I will outline a level 1-4 scenario featuring several competing factions all after the same goal in which the players will be free to pursue that goal however they want! If I have time, I will fully write out this scenario, and potentially even turn it into a full level 1-10 adventure path (with levels 1-4 focused on one district, 4-7 focused on the broader city, and 8-10 focused on a broader area).

Because I love this style, it will be a gritty urban struggle for power with a mix of criminals, corrupt cops, hapless do-gooders, and underground secret societies. There won't be a written story per say - merely conflicts, the resolving of which forming the seeds of the story that emerges through play.

Tools

Goal-Focused Design

Factions all have things that they want, and often NPCs within those factions will have competing goals! There will be guidance for the GM as to how to run each faction, as well as tools for them to play with (NPCs, response teams, locations, etc.). While not every NPC guard will be given a detailed motivation/backstory, the GM will be encouraged to run NPCs as real people who don't want to die, not (in most cases) as mindless zealots who will happily fight to the death - this means that NPCs will often flee from combat, call for reinforcements, or try to barter information for their lives, and that the GM should be encouraged to bring back random NPCs that came up earlier (I could see a random name table for each faction being helpful).

PCs will gain XP for accomplishing things! There will be some guidance as to what things and how much XP (i.e. "take down an enemy faction" or "ally with a faction"), but it will largely depend on the GM. I think there are strong odds that we'll revamp the XP system to be out of like 20 or something instead of out of 1000 as well.

Escalating Threat

As time passes, the enemy factions that survive will get more powerful. They fill find better gear, their members will gain experience, and they may even attract (or summon!) new allies. So sometimes, a given group/encounter might always be "Moderate [X]", where X is the party's level (especially for boss fights, though not always).

Other times, though, the player should feel relative level! Something really cool about Pathfinder 2e is that if you take a Severe encounter at 1st level, it will be a Moderate encounter at 2nd level, a Low threat encounter at 3rd, and a Trivial encounter at 4th.

So while some encounters or factions might grow with the party, others might stay relatively static, and will have a Level just like the players! Encounters for these will be designed for that level. I think there will be set difficulty levels for different types of encounters - scouts might always be a Trivial threat of their level in terms of raw combat power, for example, so if the party has a hard time fighting scouts that should be a sign to stay away from that faction! 

If we think of each of these chunks as a separate "book" of an AP, then there will also be escalation between books - in each case, there's a reason that only these factions (and not more powerful ones) are involved, and that the players can't just go to higher level allies to solve the problem for them. If the PCs come out on top, however, they will find themselves embroiled in something even bigger...

An Interconnected City

This adventure will be a point crawl in a city district, and each location will have clues pointed towards several others using the three clues rule (and just tons of clues in general) to always give the PCs somewhere to go, something to do. And, of course, if the PCs are stuck, they have tons of places to go to find leads, and the GM has plenty of tools to prompt action.

In addition, factions will have existing relationships and competing agendas that inevitably drive them into conflict - and that the players may be able to exploit!