That works with Type 55 and is done fairly regularly, and could be done with 665 or 85 by modifying the back (to remove the rollers, though it might be a challenge getting the second tab with such a modified back). With pack films, you'd have to pull the tabs in the dark, because there's nothing to stick the negative and positive together without the gel and the negative would be exposed as soon as you pulled it around the corner with the first tab.
With other types of Polaroid, the negative is paper with a black backing, and though it might be possible to develop it separately, it's almost certainly more pain than it's worth (probably also true of 665/85). It might be possible to replace the gel in a darkroom, but you'd have to separate the two layers (not stuck together, so that's easy), remove the old pod, replace it with a fresh one or a glob of replacement developing gel, then roll the sandwich together (in registration, in the dark) and wait for development -- after first coming up with a replacement for the Polaroid gel and testing it for correct time with a particular material.
When Polaroid finally stops selling film, it'll be a lot easier to just convert the cameras with good enough lenses and RFs to either roll film or conventional sheet film holders -- or just put them on the shelf next to the film pack box cameras and falling plate models.
