I will try to answer your question, but I need to caveat my response by saying that while I know that my title says “Forum Moderator Team”, I do not speak on behalf of MSFS. Jörg and Martial don’t include me in their planning, so I can only respond to what is public knowledge and draw upon my experience in professional software development to answer your question.
When the sim first launched, the team had bi-weekly updates for the first several releases. People in the forums yelled and screamed because the multiple updates broke their flight sims. There were public cries to stop releasing so many updates, so the team responded by going to monthly updates, followed by bi-monthly updates with world updates in between those sim updates. World updates typically [mostly] involve server-side updates to the streaming data and do not touch code. (Jörg has referred to these as “client-less” updates.) What that means is that you can release a world update in between sim updates, not touch code, and not affect anyone’s sim.
Recently, the team has taken that a step further, and there are only two scheduled sim updates this year that I am aware of: Sim Update 12 and Sim Update 13. I don’t have information for the reason for this decision, but I think part of the reason for this decision is to extend the beta periods to limit the negative effects that these sim updates have on some people’s systems.
So what do you do with the space in between? You fill it with other updates like world updates and city updates:
So why does the team have AAUs? The team that deploys those AAU changes, Working Title, is an outside separate development group. There is nothing technically stopping them (caveat: to my knowledge) from lumping the AAUs in with the sim updates. In fact, Working Title has submitted changes to sim updates in the past. However, my guess is that a decision was taken to introduce these separately because they follow a different development timeline and/or flow, and it may be easier for them to run their betas separately.
But, if Working Title were to submit their changes with the sim updates, it would not alter the speed at which they introduce their changes. It just means that they would be putting their code into different buckets.
I’m not here to dampen on your enthusiasm. I understand that weather is important to you. Whether you believe me or not, weather is important to me, too. I fly in the sim, too, and I haven’t seen a thunderstorm in a long time, and I don’t think I’ve ever seen a cumulonimbus or a cirrus cloud in the sim. But unfortunately, I don’t think that pulling weather into a separate update is going to help speed the development process.