IMO, there is a much simpler (and much more intuitive) "solution" to your perceived problem.
Just place the cut card for the second deck on top of the deck, and leave it there (don't cut the deck) until the hand in progress is completely finished. No need for different size decks, oddball dealing procedures, or anything else..
But IMO, you seem to be in search for a complicated solution to a problem that really shouldn't exist very frequently (unless the alcohol/cannabis factor is unduly excessive).