Differences between standard and enterprise SharePoint Cal's for on prem isn't as easy as it should be. Having a report of list of pertinent areas (BCS: Rich Client Integration, PowerView, video searching, data loss prevention, etc) and some sort of signifier that it is in use in your farm so you can research further, etc?
I appreciate the following:
Online potentially has less benefit (more awareness before Microsoft bill?).
Not all areas will be able to be reported on.
How the area is being used may not be able to be made clear.
Multiple areas being depreciated (Infopath services, access services, etc).
Many users may be very clear that they are Enterprise/Standard users.
Users may not want to know this data - but those that don't realise they don't need enterprise could save users money. Implement as optional extension?
Goal posts move.
You don't want to do Microsoft's job for them.
But... I've found an extensive list of the areas that someone created (not Microsoft!); I have SPDocKit; and I've STILL spent hours researching each area of what the header means and then having to go look to see if we are using it on our farm.
I'd hope that this would be a report based on a collation on specific rows from many of the reports/data you already provide.
Server licences required for farm could also be useful to view (i.e. highlight no need for SP licences for SQL servers), but much easier to understand.