These would also reflect the real world out there with Premium Economy travel booming for real travel these days. This was started 15 yrs ago, so to add a separate PE section maybe an alternative to Business class?
Being able to build & fund lounges, basic to deluxe, could be easily incorporated into the game, FF programs, higher luggage allowances, offset by greater fuel burn, as with denser loads.
Cargo would be a very interesting realism hopefully to come. Many Airlines still make more from Cargo in today's Airlines than passengers, with KLM for eg, running Combi 747;s still to Asia.
Still think we could do more with our Home bases in the games, but the work that has gone into AirwaySim is pretty amazing already, & in a constant development. I hope some of our ideas will come to reality in future games...