That's an interesting system, but I could see it being abused. Assume an alliance of 18 people where several people have 20M+ gil and Meteor or Arise drops. The people who have 20M+ gil try to outbid each other again and again till the final pricetag is 15M for the scroll. The proceeds are then distributed to the alliance (which only means ~882,000 gil to each person). Next time the group goes (assuming the guy who won the scroll even BOTHERS to attend again since why would he need to now?), again the pricetag for Meteor/Arise reaches 15M. Again, it goes to one of the people who have mucho gil. Again, the proceeds are distributed. Rinse, repeat. The people who didn't come to the group with mucho gil have to keep waiting and waiting until the incremental gil they receive from each successive payout finally approaches a threshold level where they can use their prior earnings to bid and win the scroll. (Yes, I am aware they or others can farm in the interim.) This assumes anybody who wins the scrolls actually sticks around, which in a low-accountability group where the "system has no memory" is a high hope at best.
The other proposed system "everyone chooses 1-2 items to freelot" has the same issues when only 2 items are highly desired to begin with, and the event's success depends on the continued attendance of the first few people who won freelots. Imagine how it would fly the first time someone who won an E.Body in that system says to the others "Hay guize, can't make Ein anymoar, I hav a class."