This already exists. My guild, <Dark Conquest> hosts open raids three times per week. Everyone on the server is welcome to attend.
In short, here is how loot works:
We keep track of attendance points. You start at zero. Unless you are a member of <Temerity> or <Destiny>, you accumulate points for attending raids.
When an item drops, you can "bid" your points for it. The highest bidder gets the item, but his or her points reset to zero. If no one bids, you can /random 100 for it. If nobody randoms, it rots. Other than the exception for <Temerity> and <Destiny> members, your guild tag has zero impact on loot distribution.
Right now, <Dark Conquest> is on the Vex Thal and Seru rotations and we are working on progressing to the elemental planes. We're probably about 10 people short of cracking elementals. I would encourage any and all of you to consider joining our guild, and if you're not interested in that, please consider attending our weekly raids.
Our schedule is (generally) as follows:
Tuesdays: 9 p.m. Eastern
Wednesdays: 9 p.m. Eastern
Saturdays: 6 p.m. Eastern
We have a different schedule during our Vex Thal rotation. You can see a nice summary of our regular raiding schedule and the VT schedule here: http://www.darkconquest.org/forum/viewtopic.php?f=5&t=1115
Hope to see you at one of our raids!