The question that the wording of the appeal raises in my mind is: if the warrant first presented to Lavabit related to a non-US citizen who was using the service, would Mr Levison have followed the same course of action?

I think so, how could you sell a security service with a backdoor only for foreigners? Doesn't make sense from a technical point of view.

Also, it doesn't seem that he had a problem with warrants, just opening it for everyone at once.