I'm in agreement that if they were to make anything pen and paper based, they don't even need to go as far as make any game rules. For the most part, PoE is DnD 2.0.. Which means you can just put your players from any D20 system (or any system depending on the work the DM/GM wants to do) into this world of lore. Which I will say, this worlds lore is fantastic. I'm in agreement all they would really need to make is a lore/map book with all of that relevant information, and let the players use their own systems, instead of trying to develop their own from scratch. Given the smaller market for PnP these days, and the majority of people that currently play are already in the system they like, a new world to play in would probably be a lot more attractive to people to purchase than a whole new system.