There is already a mod that let you play 6 characters.
Just let them balance the game around 4, it makes the fights faster because you don't need to add more enemies.
Please read the other topics.
Your argument is wrong.
I'd rather recommend reading other topics AND replies.
Because it's goes same as here - majority of ppl doesn't support increasing of party size.
45% of survey people are disatisfied with it and 55% are ''okay'' with it. Being okay with 4 is different of ''not supporting 6'', its means they can enjoy the game in the stage its in. For instance, I'm okay with 4 , I could enjoy the game as is, but I would totally support an increase to 6 party member .