I totally understand this want. I was an admin for years and this was an annoyance. If you have enterprise, this is a great fix. Leverage the Custom Upgrade Screen. (In admin center)
Make a sheet to track these requests, and add an approval workflow so the requestor has to fill out a form and get it approved by their manager. If they really want it, make the managers approve the cost. This way you are not notified unless it's been approved to buy/use an additional license
We have found that most times we implement this for a client, 80%/90% of people stop requesting because they do not want to justify the need and or get approval.