Okay I think I will need to use larger aircraft on my short haul flights. I am currently using A320, B734 and 738. What is the bigger economic alternative, Any suggestions?
I'd consider upgrading to A321, 737-900ER, 757-200/300 or widebodies such as the 767 and A330 to try to optimise your slots.
Nothing is wrong with using all economy. The issue, moreso for realists, is using 100% Y on certain aircraft which would need aircraft to be fitted with slimline seats, 28 inch pitch and have galleys/toilets removed.
But by all means using all Y configurations is nothing bad at all and in most situation is more realistic than forcing F/C onto aircraft.