I think that would work the opposite to the way you're planning.
The admin should have access to everything on the mac, but third party commercial applications (that require a registration key) that are registered to a different user, may not work with the new admin.
If you need those applications to work then I'd leave the admin account alone. I'm thinking of applications like Photoshop, Microsoft Office, etc.
Real Macsters don't repair permissions.
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