Navigation and landing lights, where they go? They were great in Il2, especially for on-line multiplayer landings and take offs.
Searchlights that work with the intensity they should rather than a little torch down to its last battery.
Anti-Aircraft that does the appropriate damage.
Working weather and windsocks
Rearm and refuel.
Dynamic off line campaign.Having your "own plane" with kill markings, progressive aging, weathering, repair patches etc.
Working Control tower and communications.
Coop online with Blackjack and Hookers.