Dynamic game formats

Here is something that happens a lot. In the middle of a 3-day OTB game the opponents find that they are both online and they begin to play the OTB in the same way they would a live game except that the communication of the move information is very slow because of the async nature of OTB. 

The opposite scenario is that while playing a 15 10 or 30 minute standard live game some event occurs at one end that makes it infeasible to continue the game in live format. 

In both of these cases a dynamic game format may be used so that the two players, by mutual agreement, can switch the game format. In the first example, both OTB players want to finish the game and they may be allowed to play out the rest of the game in live format. In the second example, the two players, by mutual agreement, would be able to change from live to OTB. 

Just wondering if this kind of thing is technically and logically feasible.