Is it viable to add a 4 class configuration to the game as most scheduled flights airline fly and Economy/Premium Economy/Business set up on long routes nowadays. it would be more realistic to have this as an option.
welcome 
This is not possible in the current iteration of the game - however this is feature that has been requested many times. It is my understanding that more realistic booking classes is part of the current development investigation that they are doing right now as they work towards a Airlinesim 2.0