Hallelujah, it works!
I recreated the map (again) and followed Reku's guide to the letter. Here are the things that I didn't do before: I didn't mess with any Shells and I didn't copy any .bat files. Those made the difference, I guess.
Next question: is there a way to discern whether or not their shields are up in game? The impact splash is tiny on fighters and there's no indication of whether or not the health bar is their shields or their actual health.
EDIT: I've moved on to altering unit speeds, but it doesn't seem to be working (what a surprise?) Each time I altered the "imp_fly_tieinterceptor.odf"'s Mid, Min, Max, and Boost speeds and Acceleration, it was continually not fast enough, so I changed them to huge values (min speed was 500, you get the picture), munged, and played. No difference. When I munged, sides was set to EVERYTHING, so that's not it. For some reason, it doesn't want to change...
Also, how does one make a new object, specifically, a capital ship? I want to change the way it is currently. It seems like ZeroEdit is for making whole maps, not creating an object itself. Though, as is apparent, I don't know much about it. If the answer is XSI, I have the modtools, but it looks awfully complicated.

Is there an easy way to change an object's size, too? As in a value in the ODF?