Configuring dataflow storage to use Azure Data Lake Gen 2 when there are existing dataflows

I hope everyone is keeping healthy. This is my first post here and I was hoping to talk about one of the requirements from my client and see if there's an easy solution to it. Hopefully someone here has encountered this before.

My client has 3 Power BI premium capacities. Some business users who had access to workspaces in these premium capacities have created some dataflows - 136 until now in about 28 workspaces. These dataflows connect to various sources and are finally used for reports.

As you know, by default dataflows use Microsoft provided data lake store where no one has direct access - it is considered as a problem because of data sensitivity. Hence, we want to start using a new Azure Data Lake Gen 2 account within my client's Azure subscriptions for dataflow storage.
As of now, you can only add a data lake account either on a workspace level or on a tenant level. My client wants to add it on the tenant level so that whenever a new premium workspace wants to use dataflows, their data will automatically be saved in my client's data lake store.

I know that if a workspace has any existing dataflows, we can't add the storage in that workspace. To do this, we have to delete all dataflows in that workspace, add the storage and then recreate the dataflows. Deleting the data flows and recreating them comes with their own challenges.

Hence, my questions are:

1. What would happen if we added my client's data lake to their Power BI tenant?
   1. Will all existing dataflows stop working?
   2. Will existing dataflows remain working on MS provided data lake while new workspaces will use my client's data lake for storing dataflows?
   3. Will existing dataflows automatically move to my client's data lake during next refresh?
2. Given the situation and requirement, is there a better way to do this change without impacting the dataflows and reports?

I hope I could paint you a picture. Please let me know if anything isn't clear.