Yes, you can devise a system which is a "non-forcing" pass system (0-7 or 13-15 HCP) which is perfectly GCC legal. In this case, 3rd seat however cannot be required to open. There is no rule in the ACBL which requires you to bid if you have 13+ HCP.
But as with Fred's post, you will be treading on thin ice. Not because of the letter of the law, but the spirit of which it was intended.

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