Is there any reason that a global administrator must be a licensed user?
We have a very small organization. The principal was a global administrator, but as a security matter we are going to change that so that his daily login has fewer privileges. That requires creating another account as global administrator. It would be essentially an alternative account for him, created for the sole purpose of avoiding daily logins with elevated privileges. Is there any reason not to create an unlicensed user as a global admin?
Global administrator did not required any license and no need to give that. If you did not configure any general notification or any security notification for the same. If you open any support ticket to Microsoft, Please add any other email address as it by default will give option for global admin email address @Joseph Nierenberg
@Joseph NierenbergWith regard to the Admin account, you could set it up as a shared mailbox, and provide relevant access to people who need it (or forward the emails to an individual). If you don't intend on receiving emails to the Admin account, you probably don't need to license it at all.
The Only reason i see a Global admin to be licensed is to do E-Discovery searches and View them , but you can overcome that by creating a Shared Mailbox from Exchange first, then in O365 Admin Center, make that user as Global Admin :) .(only workaround - Microsoft never recommends that)
Because organization is small, i won't recommend you with PIM solution as it will add additional costs and licensing to your Organization.