Okay, I looked into the editor js, and for the life of me I can't find *all* of the call-backs to actually replace email for spoilers without breaking it. The 'ckeditor' is minified(spaghetti, but basically fully uncommented). Or maybe I'm just looking in the wrong place? If anyone knows how to do it without installing a vbulletin add-on/plugin, hit me up, because I'll definitely fix it up.
Otherwise I'll try again another day. Maybe I gave up too soon? The width of the quick reply box and the amount of icons at the ready do leave a lot for optimizations. Not just spoiler, but twitter would be useful as hell, or punch DezBears-for-whoring bbcode, where it installs a robotic boxing glove similar to the one Data has on his belt in Goonies in front of him at all times.