I can sorta understand the urge to only keep one of an item around, but for me, it's a lot safer just to keep all of that item around. One item counting mistake and KoLmafia will wind up getting rid of all of it, and I'd rather keep the side effects of insufficient item counting to a minimum.
I should probably add this ... autosell is basically the only thing in KoLmafia that's immune to an "all but one" situation, because KoLmafia submits an actual "all but one" request. And in that sense, a separate "junk" script isn't entirely out of the question, because junk scripts primarily autosell. The one problem is that for outfit pieces, KoLmafia may pulverize them, pending on your class or the item's power, and that's where it gets dangerous.
I could add a "loss of functionality" where it doesn't pulverize, since it's better than nothing, but at that point, people may as well be writing their own "autosell -1" scripts.