I think you could adapt the rules for Mission Creation on pages 30-32 to go without the "die drop" method - or even needing to use a grid-coordinate system at all - if you're willing to approach it as an exercise in building a "pointcrawl" instead of a "mapcrawl."
I'm sure there are lots of ways to approach this; I ended up bolting on the "In the Heart of the Delve & Dangerous" rules as a starting point.
If you didn't want to add in a whole new subsystem for this, I think you could just about get there by taking the rules-as-written in the rulebook pages 30-32, with a little help from the Random Encounter table on p.16.
You would need to modify the "Mission Site Map" mechanism on page 31 though, we'd need a different engine to let us generate the pointcrawl "stepwise" as we're walking through the mission site. But we can stay true to the design intent! Those rules are meant to generate exactly 12 Areas per Level, connected by Passages and containing Features, right?
So, start with the PCs entering Area 1, and follow something like this procedure every time the PCs enter a new Area:
- Determine Area Size -- roll 1d6 to determine a "die size" for the Area (1=d4, 2=d6, 3=d8, 4=d10, 5=d12, 6=d20)
- Roll the appropriate die to determine exact number of 10' squares if it seems useful to do so?
- Determine Area Features -- For *each* of the tables on page 32 (Challenges; Encounters; Discoveries; Site Features):
- Roll 1d6 on the Random Encounter table (Result column), on page 16.
- 1 ("Encounter") -- a "high intensity" feature of that type is in the room.
- 2-3 ("Sighting") -- a "low intensity" feature of that type is in the room.
- 4-6 ("No Action") -- no noteworthy feature of that type is in the room.
- If a high- or low-intensity feature of a given type is present, roll 2d6 on the corresponding table.
- Scale the resulting challenge, entity, or discovery relative to the "intensity" rating, and flavor it according to the 2d6 roll.
- Examples:
- I roll a 3 ("Low Intensity") for Challenge, a 5 ("Nothing") for Encounter, and a 1 ("High Intensity") for Discovery.
- My Challenge Table roll is (4, 2) [Containment, Defence]
- My Discovery roll is (3, 3) [Weapon, Food / Materials] -- I flip a coin and get "Food" --
- I'll rule that a [Weapon / Food] Discovery says we're looking at military rations -- and they're the dominant feature in the room, with a comparatively minor [Containment / Defence] challenge, so let's say the PCs have found a storage closet - inside is a case of MREs (2d6 Food) -- but it's contained in a Locked Supply Crate. The crate has a low-ish DC (10?) to bypass the lock; failing the roll will destroy 1d6 Food.
- Roll 1d6 on the Random Encounter table (Result column), on page 16.
- Determine Area Passages -- Randomly determine a number of Passages leading out of the Area, say 1d3 for a room of size d8 or lower; 1d6 for larger rooms.
- Roll on the Exploration column for each Passage. Some of these results (e.g. "Choice of paths" or "loop") will need some interpretation.
- Number the Areas at the end of each Passage using the next available Area Number, max 12.
- Once all 12 Areas are defined on the "map", any new Passages will not lead to new Areas, and instead should (d10 roll):
- 0-6 -- Connect back to existing rooms (rolling randomly to determine which ones)
- 7-8 -- Offer an exit from the Mission site
- 9 -- Link to another Level
With the above approach, the Areas become a list of descriptions rather than a coordinate map, and the only thing that matters is how to move from one to the next.
Let me know what you think!