do it for those that are easy to implement/works smooth, fair enough imo!
for FTP/PS, for example, since those buttons are customizable, you could advice to put the "All in" button on X position (because theres 3 positions, 1 2 and 3), so if you do it for 1, 2 or 3, as long as the user uses the same position that SaT requires it should be all fine.
That added to those sites who have the %pot buttons as default as you mentioned, should result in a lot of sites working with an all in hotkey, and definetely people who are in my situation for example wouldnt need assistance from any other hotkey program at all ever again, and be "SaT4life" (see what i did there?)