A lot of interesting ideas. Personally, I just want something to stop the small undercuts on big items.

Most of my sales are above 1m gil. The problem is, these items do not sell often. So what ends up happening? Me and 3+ other people spend the entire day undercutting each other by 1 gil hoping to get the next sale.
People tend to buy the first item listed, even if the next one is only 1g more.

I just want a Market system where I can set the price and expect it to sell without me babysitting it. FFXI did this well, as the prices were hidden and players just made bids to "guess" at the price based on the history. I think the biggest issue with the current market is having access to live, real-time prices, without any cost to change your own price.