The "problem" is not created by the downtimes, it is created by sellers putting players on sale for a low fee under the delusional expectation and assumption that it will drive prices up.
I think it is a lousy excuse to say its the users fault if he gets hurt by unforseeable server downtime. For some players you will get much more money if you start bidding at a lower price, so this is and will be a viable strategy.
A simple solution (we will never see, though), would be to let the seller set a reserve price, so if his price target wont get matched the player will remain with the team - even if there were bids on him.