… so was my described way to distribute the app possible prior to Sierra?
You should not encourage folks to switch Gatekeeper to Anywhere, regardless of the OS version they’re running. If you want a user to run an app that doesn’t pass Gatekeeper — and, again, this isn’t something I encourage in general — have them do it via the Open contextual menu item. That’s much safer than disabling Gatekeeper as a whole.
Now, are the two options to distribute the app for me is either to tell my team's agent to do it or that we have to exchange the private key for the Developer ID so that both of us can distribute the app signed?
It’s correct that you have those two options. There are also lots of others. For example, you could have the team agent set up a service that signs apps on demand, authenticated using some other credential, like your company’s internal ID system.
I don’t have an opinion as to what you should do; you’ll have to discuss this with your team agent to see what they’re comfortable with.
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Apple Developer Relations, Developer Technical Support, Core OS/Hardware
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