I think Trainerman has a real valid point, I do think auction times affect the price of players. If we can eliminate the influence of auction time, I think prices will be more stable and less profit can be made by daytrading.
For example, with the auto-bid suggestion, more managers will be able to bid on players that will be sold when fewer people are online. Normally, those players will go below market value (on average) because there are less users online. If everyone can bid on those players, those prices will rise so no profit can be made of them by daytrading. At the same time, there should be less bidding wars because there are more players available to you.
I'm not saying it's a good suggestion, but it does address some problems.