Okay, so, we have a lot of thoughts and ideas. Here's what I gather to be a quick summation:
1. The writers would be Planeswalkers...new and original, either well-established or nascent and just coming into their abilities...ie, you may play someone who thinks they are merely a wizard, sorceror, duelist, whatever you wish to call yourself and your ability to summon and use mana for assorted things.
2. We would have an overall storyarc that deals with a large scale Tournament (with a capital 'T'), but there may be side duels going on as the characters wind their way towards and through the event.
3. Mana and the access to it would be seperate from your deck of spells, and build bit-by-bit as the duel progresses unless helped by the right spells, creatures, and/or artifacts.
4. We all agree that a limit of what spells can be used and how many needs to be in place, just need to work out the details.
4a. One suggestion is a standard deck worth of spells---if we don't count the mana, that would mean 36 spells (on average) to work with. We could go with more or less.
4b. Another suggestion was to have each person design their character to work within a given Block (eg, Mirage, Visions, Weatherlight), and that winning a duel would give access to one of the loser's sets.
5. I don't think this has been addressed, but I think we should be in a noncanon world or plane, so that we don't have to worry about conformng to an established history that not everyone will be up on.
6. While the level of sex and violence can vary, it has been suggested that it be placed in the Exotic:NC or Exotic:Extreme areas just to cover all bases.
6a. Another aspect of winning, possibly as part of claiming the set access mentioned above, would be the loser being subject to the winner's desire(s).
Anything else that has been discussed or brought up for discussion?