Yeah, I considered setting something to execute on Revit initialization, but I would need that to only execute if the session were started by this command. Not from normal Revit loading.
So if there's no way to do what I described in the OP, I was thinking something similar to your idea, since I suspect that the addin will be sequestered to the session that it was executed in. But you know, in case this isn't true, I need to get my mits on that.