Which FF programs allow TPAC upgrade?
 

I know ANA Mileage Club platinum members are allowed space available access to Premium Economy, which is a difference cabin of service with slightly different food and seat equivalent to TK comfort class or business on some airlines. Any other programs? considering switching...

For free? None.

AC offers eUps to all of their FF levels for TPAC but....... Depending on your level this can be very difficult to impossible to get. Also you cannot upgrade from their lowest fares regardless of your status. You need to purchase mid to high level Y fares just to have a chance.