Something I have noticed is that RF2 is only able to show high-altitude (cirrus type) clouds, but low-altitude clouds (cumulus type) clouds should be there as well. This is not highly important for RF2 but I do think it would add to the feel.
I remember Tuttle (I think) giving a winky smiley when someone asked about it before. Makes me think it is something they already have planned for the future. Then again, it's late here XD
There are some libraries out there that could be used. For example - these guys have been working on cloud system for 7 years: