Currently, styles.ini contains ordering information and a user-friendly style name. I feel that while the former is a user preference and thus belongs in a file like styles.ini - or perhaps even in a file in the "settings" dir, rather than inside "styles" - the latter is an attribute of the style itself, and should be defined by it.
I can see two ways of doing this:
1. Introducing a "style.nxmi" file that contains this information, and any later style-specific (not theme-specific) information. Downside is the extra file.
2. Adding it to the "theme.nxtm" file. Downside is that this would disallow having a style that contains pieces, but not a theme - not sure how common this actually is though.