I can just echo the "I would be interested in this" that Rechan said.
They all sound good, and I don't really want to influence you to do something you might not find as fun or interesting.
Having said that though, I think a lot of people a thirsting for terrain and hazards. I don't know if doing a whole book on them is possible (I find it harder to come up with ideas for hazards than monsters), so it might be more appropriate to add a few in each monster book? Something that fits the monster theme of course.
They all sound good, and I don't really want to influence you to do something you might not find as fun or interesting.
Having said that though, I think a lot of people a thirsting for terrain and hazards. I don't know if doing a whole book on them is possible (I find it harder to come up with ideas for hazards than monsters), so it might be more appropriate to add a few in each monster book? Something that fits the monster theme of course.