Plugin ImageMetaData enables display of any meta date as any type. For example, I can configure in INI file jpg-comment.ini of plugin to display GPS lat/lon as pretty-printed strings:
You can leave h, but use the specified formula for it. This will be a bugfix. And add d, which will match the current implementation of h.
In any case, people will see this in the change history and take appropriate action.
For compatibility with the old settings, you can also make h and d work equally, but remove h from the options.
You could also add unit settings to exif.lng by linking the old h to the new name.