If you think that it could possibly grow to more than one person -- even if it's just two or three people total -- I would recommend creating a Group to place the person in. It's okay to have a Group that contains only one person. Especially if that person is expected to change i.e. they get replaced with a new person several times a year, like an intern. Then set up the permissions for that Group for each of your Projects that need it. Done! Then the only maintenance you have to do is update the Group when the current person gets replaced or if you add an additional person.
You set permissions individually per Project. Now, to make like a bit easier, Tableau will populate the permissions of new Projects using the values in the Default Project So set up the permissions as you would normally like to have them in the Default Project. The next Project you create will assume those Default permissions. Naturally, you can make changes to the permissions of any Project at any time to fit your needs.