Hi Barrote,
Actually I liked your point. I also though about another thing that can add a little robustness to your proposal. I think that besides the button it makes sense to create some penalty to any user that want to press that button.
When we sell a player we receive only XX% of total value 'cause we must pay taxes. So, if that button ever exists I think it's fare that we got charged with that tax percentage:
Example:
I set on market "Player X" and the last bid was $1 000 000
I will receive 97% and I will pay 3% of that value
So, in case I pressed that button "Take player of the market" I should be charged with 3% of $1M
Note: and of course, we must understand that %'s change according the actual rules.