It would be a nice feature for dictionary developers to be able to see all valid words recognized by the dictionary they are working on. As far as I remember it was possible with hunspell (unmunch) from the command line.
The code for this (munch, unmunch,…) is in the command line tools not in the Hunspell library itself. I'll take a look at it with the next version of NHunspell and will integrate it if possible.
BTW: I wonder what kind off application you're developing so that you need this in NHunspell? Dictionary developers can use the hunspell command line tool to perform this tasks. If it is not a secret please post something about the application you're developing.
I'm working on a tool which can generate hunspell dictionaries for Turkish from a corpus automatically. Because of the very complex and agglutinave morphology of Turkish it is almost impossible to develop hunspell dictionaries by hand.
I'm the developer of a Turkish NLP library written in C#. I'm using this library for generation and NHunspell for testing purposes right now.