In short, the point is to make the adventure useful to as many people as possible. I’d considered statting things out in multiple systems, but realistically, the vast majority of people who would run the adventure would do so in d20 – and, of those who wouldn’t, the vast majority are likely familiar enough with d20 to convert it.
Instead, I’m thinking that I will write in support for a wide variety of gaming/campaign styles rather than game systems.
Want to run a political game? A humorous game? A dark, morally ambiguous game? A game with evil PCs? An old-school, trap-filled dungeon romp? A pulpy swashbuckling adventure?
My current plan is to provide advice and encounter alternatives to support as many of these as I can.