Ok that's gonna be a li'l trickier. I think the way to go about it would be to:
a) modify the current 'elseif' admin argument, specifiying that if their U_Status is admin AND if their U_Username is 'admin1' OR 'admin2' who gets full access, then they will receive the list of full options (already given).
elseif (($user['U_Status'] == 'Administrator') && (($user['U_Username'] == 'admin1') || ($user['U_Username'] == 'admin2')))
b) create a new 'elseif' admin argument specifying that if their U_Status is an admin, but their U_Username IS NOT 'admin1' OR 'admin2' who gets full access, then they will receive a list of limited options (which you'll need to specify, just cut & paste the full list from above and remove whatever you don't want them to have).
elseif (($user['U_Status'] == 'Administrator') && (($user['U_Username'] != 'admin1') || ($user['U_Username'] != 'admin2')))
Obviously...
admin1 = your username
admin2 = the other admin's username
Do you know how to go about implementing these changes now, or?