...These fields don't show up in the Empeg database ...

Uhmmm .... I'm not so sure that's true. Are the *1 files a consequence of database/playlists/tags or is it the otherway around? If the *1 files _are_ a consequence of database/playlists then anything overloaded into the *1 files would be lost on a sync (think 'Rebuilding database'). If database/playlists are a consequence of *1 files, then the overloaded stuff in *1 files would find it's way into database/playlists. I guessing here, but I think that there would need to be an addition to tags, so that an appropriate label for the new (overloaded) field would be available. Would overloading a new field in database/playlist/tags confuse the current player/emplode/emptool stuff? Hmmm ....
FWIW: I recently discovered that my player's database had duplicate field entries in the database file. In this case it was seemingly harmless, in that it was the codec field which was duplicated. To fix it, I just wrote a small program to read in the old database/playlists files and write out new database/playlist/*1 files (minus the duplicates, of course). I think i'll try adding a couple of fields to my db and see what the player does with them (hopefully nothing).