Hi,
I'll start with an example.
In current GW#2, it's almost 1975 and there is no current flight between Auckland and Western Europe. So where do the pax wanting an LHR-AKL, CDG-AKL, MAD-AKL go?
Nowhere, they stay at home.
While in real life, they would look for a transfer using 2 different companies. Or at least part of them.
So as we're going deeper into dynamic demand (even if CBD for pax is not yet implemented), at some point it would be really interesting to divert a part of the pax of, say, LHR-AKL to go through some other airport that serves both LHR and AKL.
If we consider the current situation, they could go through SVO, DMK, HKG, YUL, ATL, etc.
As only a part of the initial demand would divert, and then be spread over those said airports, the increase in demand would be rather small (unless there is only one airport serving both cities), but it would still be quite realistic and interesting. That would insert the notion of base demand and potential demand not only for a catchment area of max 200 km radius, but worldwide.
Considering this on smaller routes (LH/MH), this would also reproduce quite realistically the hub and spoke model until somebody flies point to point more efficiently.
Base demand would be the point-to-point, and potential demand the hub and spoke. And in this case potential demand would be calculated from non-served routes rather than from all possible connections (only the non-serving of a said route would trigger the effect and insert that route's demand in the potential demand calculation).
This would probably be a mess for the servers, but surely something to add on the longer run.