Ok. Let's put it another way:

4 party limits gameplay for those who play multiplayer with 4 players.

6 party limits no one.

4 party = current stats and so forth. No change.

6 party = option to use proper D&D stats. Change doesn't hurt or limit anyone.

So why not give those of us who want a 6 party the OPTION to have it and to have it with proper D&D stats so it isn't so easy it's boring? Why fight it if it doesn't limit or change your gameplay in any way?