it's, IMO, indeed the open and very nicely structured model used in their configuration files, used by the simulation engine to do perform various tasks...
The other big point is the good sense in the IPACS Team - they're trying not to be forced by the nowadays typical temptation to rush everything and get profit fast... They take their time to cautiously evolve, one good step at a time... It's up for the users to understand / accept that pace, knowing that things will come, with time, but without a precise schedule, that would be dangerous / impossible to set for such a small Team.
Things that come to my mind regarding the future of AEFS2 as opposed, for instance, to the future of X-Plane or MSFS-derived platforms, are the possibility of building from scratch various modelling approaches to systems simulation, that could be used alternatively, depending on the use one want's to make of the sim.
Some of those systems could be core ones, like the Weather engine. That one in particular, given my area of work IRL, and the fact that I am a long time glider fan, is a system that would certainly profit from a detailed, revolutionary approach, and I'm not talking about the graphics, which so far are evidently not a problem for IPACS :-), but the way the atmosphere could be modelled, introducing for the very first time in the short history of flight simulation games such important effects like that of Moist, Geopotential Height modelling / non-ISA pressure and temperature "lapse rates", etc...
My feel when I start AEFS2 is mixed. There's the WOW feel, but since I was "created" as a simmer running ATP, FS2, 3 and then 4... and still using ELITE for IFR, or Aerowinx for the most advanced b744 simulation available for a PC, graphics aren't actually my main concern.... There are still few things to occupy my attention as a virtual pilot, very few systems being simulated, no AI or Traffic, etc... But! there surely is the Potential Energy to get it running - it's probably just a question of learning to be patient and Wait....
Looking fwd for June 15th