Yah seems like it, i dunno why they don't comment this idea even though its a really great and convenient idea.
The problem might be that this idea or something similar has been proposed a few times in the past, and nothing happened.
In my opinion the biggest problem is to avoid that the buff shop is used by players as a "stamina reserve" and, at the same time, make it so that noone lose stamina.
I could create 100 auction for DC at 1 FSP, noone would buy them and cancelling the auction i would have the stamina back after 48 hours.
or
for example, if buff auctions expire automatically if the player is offline, i would lose my stam with no gain, so I would not use the shop in the first place and continue to sell buffs via shoutbox.
The simplest solution I could think of is :
Create some "Stamina Storage" where players can ONLY PUT stamina and not take back. (The opposite of how the reserve stamina works) .
It will be up to the player to transfer stamina from current to Storage, if you transfer too much.... well, it's your problem

When later you have to create the buffs to sell in buff shop, the stamina is taken from this Stamina Storage and not from your current stamina.
If you cancel some buff action (if you can do this at all) of if the auction expires (if they expire) the stamina goes back to Storage for use in creating other buff auctions.
Would this be possible ? You have to ask someone who knows how to write code...