I think this system have some weaknesses:
1. What is with players who are just online at specific dates, i.E. "weekend players" they could watch player on saturday/sunday but are unable to bid on them.
2. You won't have people wh are checking the transferlist for cheap players, so if not at least observers aren't able to pay a normal price the player will get sold for a very cheap price - with the current system their will be bidders who will raise the price at least a bit because he is so "cheap".
3. if you recognize, that they are just two observer who are looking for the same two player, they could arrange not to bid for one of those player.
4. you get inflexible, when you had to react to a injury or a big transfer of the opponent.