Thanks for the reply! You're right, putting my focus on just a few elements is probably a good way to manage my overwhelmed feeling. I already feel better about this endeavour :)
I've read small business, and honestly, this is the #1 thing that got me to want to run this. I'm envisioning a full blown worldhopping thing where the PCs get to visit the homeworlds of the three NPC guides, and in each world there'll be some sort of fun rules mashup happening. I immediately recognized each NPC's world of origin, and my first thought was, well, this is the Disparateum, surely we could visit them there! And so each act would play in a different gameworld and I'd come up with some cool way to blend in some iconic rules from that game, similar to the NPC traits already there.
In my mind, this wants to be a somewhat bigger module with three arcs, which is why I don't want to immediately start with it. Dabble before you dive. But eventually I hope I can make this happen! I want to send my players into a world where everyone moves in alignment to a huge omnipresent 5-foot grid, and nobody ever comments on it because it's just normal. And when the PCs choose to ignore the grid and use their own rules, all hell breaks loose. :D
In any case, thanks again for the advice, and I'll report back how it went after our first session!