It would be nice to be able to manage a customer across multiple workspaces. At a minimum, setting a tag on a customer in more than one workspace would be useful for more closely tying together related businesses that are not all in one workspace.
Today this requires both workspaces to utilize Zapier and Webhooks to keep any data in sync between workspaces when a single customer is in both workspaces.
The more features and complexity that we get in ClickFunnels, the more likely multiple workspaces will be used to support a single business moving forward - and shared customer records would make this even more convenient.