So, my take on this is that it's really fantastic and brings alive the career mode. However, the random weather is just that - random weather. It could be stormy in practice beautiful sunshine in qualy and fog in the race. It's clear why SMS didn't implement it because it needs a control the flow of the weather.
I was thinking, it would be great to set up say 20 or so weather lists and then assign those to each race randomly - would that be possible? Each year the races could all be randomised again but the weather slots would tell a story and not be competely random. Does that make sense?