Regarding mod manager and UI integration I for start would like something simple as same component naming in mod manager and in game or at least ability to find component in mod manager by their UI name.
I wish there was an ability to delete unwanted skins, since I banned fictional skins and skins belonging to a different car from my PC - never thought what a PITA rF2 and their inflexible rfcmp files really is - because if I can't remove them then the entire mod pack has to go.