Here is a point to consider. I have a "Provider" account set up. I am Importing a massive amount of data, old paper charts. So in order to prevent ALL of the old paper charts from populating my Inbox, my staff uses the Import feature while logged in as the Full Provider called "Scan Scan." They have permission under this user to simply import, and I don't have to sign off on these documents.
However, when they import new documents like labs and CT, they do so under their own name such that it's copied to my Inbox. AC cannot "see" another provider under my license.
However, if for some reason they could find out that information (by either reading this post or by somehow spying on my computer), and if they further ask me to spend $200 for a provider account....I think a simple explanation as to what I am doing and why I'm doing it will suffice and they wouldn't charge the $200.
I further believe that the poster of this thread could make a new Full Provider account and call it "Dr. L Tenens." Let your few Locums per year use this account. I hardly doubt AC would charge you $200 for this. If they could even see it, which I don't believe they can.
I believe their update feature simply checks which version of the AC program you are using, not WHO is using it.
Therefore, I wouldn't worry about it. Do whichever is easiest for you.