edit: What I'm finding, after countless trials, is that the mere presence of Symphony's output pack in the data directory stops my test mods from loading at all. Even if it is removed from the user script, it still gets referenced and mod loading seems to halt. This is true also if I run my test mod as a movie type. Otherwise, every simple test mod I've constructed works as expected, whether it's removing a unit from the base units table (or not) and adding it back via a single row supplementary table, or modifying the base table directly. I have to change Symphony's output file extension to effectively hide it. I don't know if that's revealing of anything other than possibly the sounds_packed directory may be a special case in the loading scheme.