You can create a group with almost admin privileges and call them junior admin or something similar.
Go to Admin -> MemberGroups -> Add Membergroup.
Membergroup name: "Junior Admin" or something similar.
Permissions: by type - "Maintenance"
Leave the other settings they should be fine.
Then under Admin -> Permissions, you can click the "Modify" button for the newly created group.
You will find that because they are a maintenance group, they can have a lot more privileges than the global moderators. You can now restrict their permissions easily.
There may be certain permissions which they cannot have, but they should be able to have most of the permissions which a normal admin has.