Already menioned but will mention again:
* Driver Swaps (If this is included successfully, SimBin will dominate the online leagues for sim of choice)
* Full working dynamic weather
* Damage realistic including things such as blown exhaust manifold, valves, pistons, over heating, brakes etc. Would be great to get oil build up on windscreen etc like NR2K3.
* Full animated pit crew, that make occational realistic mistakes wheel nuts wont go on, no fuel coming through need to swap refueler etc.
* full animated grid, with crews, grid girls etc.
* ability to set a full pace lap to line up for standing start or rolling start.
* realistic and adjustable pace car settings.
* multiple tyre options
* LTT that we had in GTR2 except even more realistic
* more cars on the grid at least 30 or 40
* ability to easily rearrange and make settings to add weight or remove weight from the drivers finishing positions from the previous race.
* realistic broadcasting options with overlays of drivers names, splits best times etc and nice camera swaping opions so leagues can have a spectator live streaming the race
* Sorry to tell you this SimBin but iRacing have made Lazer scanning a must this days I think as by far the best tracks for rFactor are also the laser scanned ones.