put the ini in side your p3d, then use my code from here to work with it: [Working with files, inside p3d and not) (specifically, join the pathPrefix onto the beginning of your file path). Then it will be able to find tiles in your miltifile p3d.
If you need to modify the file, look at some place to see if it exists, if not, load from the p3d, and when saving, write to the place you check for it.