Okay, I'd missed @twobob's stuff because I mostly don't care about GUI stuff, but doing it the Hard Way (wmctrl) still kinda works.
The resize (as in, twobob's original example) is a bitch because the values are device-specific, so you'd have to parse the query output first, but it works (at the expected cost of causing a re-layout).
On the other hand, hiding works over here on FW 5.9.7.
(i.e.,
wmctrl -r L:C_N:titleBar_ID:system -b toggle,hidden).
The catch, of course, is that this is a third-party tool that's:
* Old, which might in turn end up affecting my next bullet point... (EDIT: although, it's in Portage, I happen to have it built on my system for some reason [EDITē: dropbox], and the only patch needed is for 64bit compatibility).
* Requires X11 libs, which requires going down a rabbit hole of dependencies.
Which means it's proooobably not going to be happening
.