I could see some problems with an early signing period, but in the end, I think what it would do is it would force both coaches and players to start taking the idea of offers/commitments more seriously. Coaches would make fewer early offers knowing that they may want to wait to see a guy play his senior year before committing 100% to an offer. A lot of coaches make offers to guys that they may not be 100% sure about solely to be sure they are in the boat with the player just in case. If they later re-evaluate and determine they aren't sure about the player, they can either slow play him or remove the offer.
An early signing period would eliminate a coach's need/ability to throw out offers to guys they aren't 100% set on. At the same time, you wouldn't see guys like Robert Elliott making a commitment so early in the process, and even if a player like that chose to commit early, you'd find out that it wasn't a serious commitment the minute they chose not to sign during the early period. It's like when Scotty Hopson chose not to sign with MSU during the early period. When he did that, you found out that he wasn't serious about his commitment. To me, that's a good thing for coaches, because they then know that they have to treat that player as if he's not committed. Therefore, it leaves the coaches time to start looking at other prospects at that position, while also knowing that if they want that particular prospect, they better continue to recruit him as if he's not committed.