Our partner has two use cases to switch over ACM hub clusters and also migrate some spoke clusters between two hub clusters. 

We have created following document to list their use cases and some limitations observed during these tests: https://docs.google.com/document/d/1K-Azx7M3U_nLQCNDwn7xTVv12aY8B6pIfJ5CqYqnpOM/edit?usp=sharing 

We need some review from ACM team to list any other limitations may exist during spoke cluster migration and review of the scale in process that is applied in spoke cluster after hub cluster switch over is completed.

ACM version used is 2.11.0