I hear you, but my suggestion, if not hitting other constraints (one of them is 1500 project per portfolio), would be easy to implement for future employees because you would just update each project template to add projects created from it to the “All” portfolio. For existing 500 x n projects, that would be a one-time effort of a couple of hours.
Note that I updated my earlier reply to make a couple corrections.
On another note, if you ever reconsidered this design, you might benefit from my workshop video (free) in the Asana Academy:
I think from what you’ve described, you’d have a much easier go of it if each employee was a task, not multiple projects, but this is only based on the limited info I have.
Thanks,
Larry