I know many people, myself included that have standards and bantams mixed together with no problem. The problem th OP will have is roosters fighting. I have two bantam Cochins and I can assure you, they are not at the bottom of the pecking order. I do have a lot of room, a 6 by 22 pen plus free ranging a couple of hours a day for 7 chickens. ( one standard Roo, 4 standard hens, and 2 bantams.) But I don't see any problem with mixing standard and bantam hens together.
