The numbering of paragraphs is a great idea. If this feature was added, more people would use this feature in a legal brief context. I think this is a case where if the feature was added it would attract more users.
As a programmer, I know this should not be too hard. I know John M (the author of Pandoc) is an excellent programmer simply by the results he gets. It just depends if he has time to do it.
There are websites where people can vote on features for the next release. I could dig one up of the Pandoc author wants to get votes on new features. Those websites are normally free.