Would love to have a cargo heavy like a 747 or 777. Almost all 747 fleet now is cargo and trying to simulate cargo flight with passenger windows is a bummer. A third helicopter would be great too - any heli, don't mind which, military or civilian.
In external view this sim is gorgeous especially at major airports. I do all my fixed wing flying out of cockpit now on autopilot/copilot following SIDs and STARs (I just taxi to and from the runway) and the external views and sounds are fantastic.
My two bobs worth.