You can create an advertising account as a company, but you have to do this with an email account (hotmail or outlook) which is bound to an individual. When signing up for such an email account you have to give your birthday. Default you are assingned the role of Super Admin.

After you have created your advertising account, you can go to the Users tab in the Account settings and invite other persons to the account. This is where you could invite the marketing manager email address. In the user settings you can change the role of this new user to Marketing Manager. There is only one caveat, and that to access this Marketing Manager account, you first have to create a new, or attach to an existing email account, which forces you to add a birthday.

Therefore adding an anonymous marketing manager account is not possible, but as a super admin you can easily add and remove individual marketing managers in the account.