This feature request is working its way through the backlog queue. No new details are available yet.
-WarrenTarik Kranda commented
We are also seeking for Scenario A;
A1: I would not expect Teams to auto-generate all folder structure automatically, since there are folders good for Teams integration unlike some other not good candidates to integrate. It would be nice to be able to have a list to select some of them as a step of New Teams Creation Wizard. So this would be up to user just by selecting All or eliminate some of them. For new folders which will be created on SP site by time, there maybe an option to bind them or unbind them to Teams.
A2: 3. This is not so cruical for us at the moment. Integration of Teams to existing O365 group resolved the ciritical part for us at least. We are using O365 groups mostly now.
A3: I did not experience Create Channel API yet, so can not give correct scoring.
\TarikTarik Kranda commented
I would also like to inform that afterwards of your team creation, you can go to Office 365 Online and remove that office 365 group created behind. But in this case, you are not able to use some functionalities of Teams such as file sharing and you can not get email address of the channels for that team etc. Some functionalities of teams are directly attached with Office 365 groups. It would be great to have this functionalities with no binding to a new or existing Office 365 groups.
Performance has been and continues to be a big focus area for Teams. One main area we have made improvements in is responsiveness for the most frequent user actions of switching between Chat, Channel, and Activity. We are also focused on reducing resource consumption and application load time. More improvements are on the way.