Hi John,
This is really a unique scenario. Basically PM is used by the Administrator only for promotion purpose but Delegate Administrator ( Non-Admin ) and also use this. Either Limit the access of the users by following below KBA or as per my knowledge there no other way.
Yes, If you use any external/third party tool may be but in that scenario it will fall out side the support boundary of SAP.
KBA : 1785929 - How to set rights on Promotion Management for a user
KBA : 1712888 - BI 4.0 - Delegated Administration rights for Promotion Management
Regards,
Mahak