To my understanding, "% Hist. Value" is based on (of course) the historical of the item + the current buyout price for a single item (irregardless of the stack size of the auction).

If I sort ascending on "% Hist. Value", the auctions will be listed according to "most bang for your buck if you choose to use the buyout function".

However, more often than not the bid-buyout gap is significantly different across the different listings of a given item. If I'm interested in finding good "bid deals", I currently don't have a good way of sorting the auctions to list them according to "most bang for your buck if you choose to use the bid function".

Would it be possible to add a sort that is based on the bid price which would help me find good bid deals?

In the latest version you can right click the percentage column like the price columns to toggle between bid and buyout.