Theese seem to be the predominent opinions of players (or, at least those in my area) of how we could make decks more varied than with just the ban list alone.
The big two that I can think of are:
a) have it work like in the video games.
1. Give each card a numerical value
2. Make a limit of how high your deck cost can go
3. Make it so that as you progress your max. deck cost DOESN'T go up (unlike the games)
4. Make it so that the value of cards in your deck change depending on if you have certain other cards in your deck.
Granted, the judges in the tournament would have to do some extra math, and someone would have to decide on the values of the cards, but it would make things interesting.
The only problem is that it isn't very practial. It would take forever. If you had a computer program that assigned and checked the values for you, that would speed things up. And maybe have people send decklists ahead of time and run them through.
Or, (and this is the better one in my opinion)
b) You could make it so that you could only have a max of (v)rares, (w) super rares, (x) Ultra rares, (y) ultimate rares, and (z) Secret rares in your deck (and with the reprints, each card would be applied to max. of whatever the rarest form is).
(Hey cool, VWXYZ)
If say, 10-15 of the cards in your deck had to be commons, then that would really vary things up.
Just something to think about. Though, I'm sure if we all put our heads together, we could come up with something better.