That's the frustrating bit of Steam as a mod platform. Do you plan on releasing it on something like Nexus down the line? It wouldn't surprise me if the Xulima crowd on GOG is relatively sizeable and generally more hardcore, so there might be quite a few users there interested in a mod like this and it would be easier for them to get it that way.
My general impressions of Nexus have been:
1: If you have a crunchy, non shiny mod it will not gather any interest.
2: If you're modding a game not many people mod it will not gather any interest.
3: If you don't include safeguards you will encounter mod theft, 120% in any project that required actual time and effort. I already have actually. Some idiot casual got mad he couldn't beat the last boss and stole the mod. Yes, really. Of course he also whined about "unfair bullshit crits for 70"... from an enemy that only uses telegraphed easily avoidable attacks and every other person put their marked character in rank 3 (out of range) after seeing what happened when they didn't once. Not dealing with that bullshit again, I have enough idiots between the developers of this game and their stalking fanbase already.
It's mostly just frustrating to see potential go to waste. The presentation of this game is really good and enough to probably make at least an initial playthrough enjoyable, but the mechanics do not look deep enough to have the game grow into a classic. They really need to go back to the roots of what makes dungeon crawling fun and implement features that support this and look at how other squad-based games use perma-death without making characters feel too expendable (Mordheim and Battle Brothers might good sources to draw inspiration from), while tweaking the content they already have so that there's worthwhile variety.
Currently, the developers are busy with low quality comics instead of working on their behind schedule game. Static, written/drawn narratives suit their talent sets far better than actual games, and if you lock Chris in a box and make him draw on demand for you you might produce something passable. Just don't let him near design and file a restraining order against Tyler's design.
I mean there's an expanded map generator thread in which Steam user ZiN draws an expanded map showing multiple routes, a wide variety of events, scouting revealing the composition of enemy parties and a number of other things. That thread was buried in responses of that seems difficult/work intensive for the devs. Which I guess it is given that it involves making a walking simulator an actual game but I don't see why that's a valid cause for rejecting it.
Just spitballing, but I'd suggest something like the player coming into dungeons with zero knowledge of the layout, with only the hallway to the next room(s) being partially visible and scouting allowing you to see more of the map. Giving effects to succesful quests for after you've completed them and making them more in-depth, such as completing a scouting mission having you start the next mission with the map partially filled in. Dungeon shortcuts and other interactions beyond combat and traps. Different approaches to dungeon crawling, like allowing for small parties of sneaky types that hide in the dark to avoid enemies, which is stressful but potentially highly profitable if the dungeon would normally be too tough for you, or makes for good preparation - scout a big dungeon with an experienced Highwaymen, then come back with a your heavy hitters while knowing where you need to go. Having being able to escape contingent on having an escape route by having leaving the dungeon requiring you to reach the exit, plus enemy types that move around (so you'd have to be careful not to get cut off while exploring in case you want to leave). Larger dungeons in general, so that choosing when and how to engage becomes more of a factor. Finding imprisoned, lost, injured heroes with abnormal quirks and skillsets that you can recruit. Basically, in addition to improving the combat, make the dungeon crawling itself on the whole more fun in ways that don't necessarily involve killing. That way you break the tedium and alleviate the grind by giving ways to use your party skillfully, rather than just butchering your way through. That had been my hope for the game, but it's unlikely that it'll still happen.
This is actually pretty close to something I proposed in the Steam forums.
Instead of having every mission using a small and simplistic random dungeon, create one big but persistent dungeon for each region (ruins, weald, cove, warrens) and dungeon level.
You start mapping out the respective dungeon and eventually discover stairs that lead into deeper (i.e. more dangerous) levels. At the deepest level of each dungeon flavor you'll find an entrance to the Darkest Dungeon (endgame).
Making it persistent means that it can be much more complex (secret rooms and passages, locked stuff requiring special keys, etc.).
Missions and quest types can be made dependant on each other - scouting missions reveal more of the dungeon and placement of enemies, combat missions reduce number of enemies, boss missions to kill dangerous enemies and maybe unlock special things (e.g. a key to the next level). Basically very close to what you suggested.
At this point it's obvious that this will never happen, though, but I think it would have made a better foundation for the dungeon crawling aspect.
I would also have balanced it in such a way that the entire game can be beaten with a relatively small amount of heroes (e.g. a roster of 8 or such) within maybe 10-15 hours, making it something which you would like to do several times with different sets of heroes.
The very early builds (well before prerelease) actually had Fog of War, no idea why it was removed.
What you describe sounds like an excellent game, and it's why when I saw a game called Thea, The Awakening my first thought was that if this were an actual game and not a walking simulator it'd look like this. Thea also has the unique themes, the Roguelike elements, the tactical elements, the resource management, the squad management, the hamlet (village), and so on except... it actually does. Enemies don't just passively sit there and let you farm them, they will attack you. It does a much better job of making you feel surrounded and oppressed, yet capable of fighting back than this game ever could. And night? That makes enemies more aggressive. Far more a danger than a mode that just buffs your crit and loot.
Instead we get an "endgame" consisting of grinding through a fifth dungeon just like the other four followed by grinding out a clone team so this can be done 3 times. And there's still no lose state, so it's only grind until you win with a game so simple a script could run it. But hey, it's going on mobile for a reason!
Oh yeah and fun fact. You frequently see a lot of whines on the Steam forums about RNG, typically involving extreme crit rates. Enemy crit rate is generally 20%, so 4 crits in a row are 0.16%, or 1:625. Given how grindy the game is, odds are this will happen at least once. I mention this not because people do not understand statistics, but because Red Hook actually is manipulating statistics behind the scenes. Just not in a way any of them are predicting.
A while back they made some hidden changes that manipulate RNG. They said they were doing this but never described how. One of the ways I am 99% sure they are doing so is that if you select your actions very quickly (less than 1 second) you have a much higher than statistically possible chance of missing your attacks. This is very obvious if you have perfect accuracy because you will miss much more than 10% over an extended timeframe. Now consider both that with how grindy this game is, adding a 1 second delay on every action adds hours of waiting on sluggish animations, and also that someone just interested in getting on with it, or not paying attention, or distracted by Twitch chat, or just casual and not thinking through their moves will just hit the next button quickly, resulting in stupid deaths and developer validation and of course, more grind. If only they were this creative about their actual game mechanics than they were about diluting their content in the style of cashshop MMO Dungeons and Dragons Online and its True Reincarnate feature!