The clouds look nice but a huge missing aspect is that clouds create high and low pressure zones that can cause you plane to drop or climb 1000s of feet, for example thermals under cumulonimbus clouds. Also, flying in clouds, there should be substantial turbulence. Furthermore at different alts there should be different winds. If clouds are moving like a low fog bank, there should be a wind that is causing it to move.
This would cause the game to become much more realistic and add a whole new dimension to combat.