I just thought of a rather grace-less solution to this. BOB could have a button that says "Snap for other team." I know that BOB snaps can be read outside of [team] chat. For example, I just posted a public snapshot in this Game 12294725
So, given that BOB has this ability, it could also be set (very carefully) to take a snap of ONLY territs that the other team can see. Thus one team before starting their turn in a fog rule game could take a partial snap for the other team. Now, I do recognize that there is at least one deficiency of this:
Territ A bombards B. Territ B one-way attacks C. Team 2, who play second, owns territ A and C. Team 1, who play first, own B. Team 1 has no territs that can attack or bombard A (A is behind the fog). On the turn, Team 1 attacks from B to C.
Snap before turn? BOB would have no way of knowing to "report" or "snap" the ownership of territ A because it has no way of knowing whether Team 2 can even see it. It can't even tell whether to include Territ C in the snap because giving away that Team 1 can see Territ B tells Team 2 that they have C (if no other Team 1 territs can attack B). This of course is not a problem in the given instance, but if A was neutral, then Team 1 would not want B in any sort of snapshot.
Snap after the turn? BOB could maybe check game log and tell that territ C belonged to Team 2 before the turn, but again the question of whether and how to report B remains.
This seems to me like it would be a good thing to put into BOB, as long as BOB checks that there aren't any bombardments possible in the game, but it could cause problems on a map like Waterloo or Stalingrad, and would most certainly be unwise to use in All Your Base Are Belong To Us. Perhaps BOB could error on the side of disclosure, but a warning could pop up: "You are attempting to take a snapshot for the other team on a map that contains bombardments or one-way assaults. Doing so may disclose information that the other team cannot otherwise see. Proceed with caution."
At the very least, this addition to BOB, if used in appropriate circumstances would allow a team to take a turn before 12 hours and not gain (or suffer) a competitive (dis)advantage. BOB already has the capability to determine which territs cannot possibly be seen by the other team (they're the ones with the boxes around them). So, this could theoretically be worked in to BOB.
Other potential problems include people accidentally snapping for other team when they don't mean to. Also, this relies on the other team to take the snap (but the benefit to them is that they don't have to wait 12 hours).
**The way I did this is to disable BOB and copy and paste the "snap:: ....." junk that is in chat when you don't have BOB on.