Why do people even bring up this "360 membership argument" there is no argument, you can play FFXI on a free silver account.
Just because you can play FFXI on a silver membership (and you have to be pretty out of touch with the history of the game if you don't know that SE had to battle M$ to make it that way), doesn't mean that they are going to easily concede to ANOTHER game that doesn't require their money sink membership.
If anything would cause SE to pause when considering releasing this for the 360, that would be it. We are potentially looking at a game where the only fee to play is paid to SE on two other platforms, and one of the only two games you would be able to play online with a silver membership (FFXI being the other). Are there any other MMOs on the 360 that work over silver?
Someone would be losing money, whether it's SE paying a royalty to cut out the need for us to have Gold (cost would be passed to us somehow, and would be shouldered by those who aren't 360 players as well which isn't fair), or us having to get the gold membership which wouldn't please anyone who doesn't play Halo or other 360 online titles and doesn't see the value.