No, you can't get vouchers in advance for a different weekend. You can get them on the Friday preceeding the weekend. The whole purpose of this is so that everybody gets an equal chance to get in and it cuts down on the congestion.
Each person is allowed to get 2 vouchers. So, if your buddies get there before you, they can get your vouchers. That's why they need your plate number.
If you understand the system, it works quite well. If you're dune ready, it takes a whole 5 minutes.
OH, and your statement about this "new" system..... it's not new. It's been an established system for years.