I like this but I have another suggestion: Most players use a tweaked but more or less stadard anti FG rainbow deck. That's a bit boring. So why not use this system?
We don't need 9 Gods simultaneously. What if we try 2 Realms in one Challenge this way:
On Thursday, Chris starts the first Realm with 3+3 Gods. 3 very strong like the ones in JFF2 (or a bit stronger) and 3 with the same cards but weaker effects. For example we have 3 Life Gods, Big Bang, Opus and Tardis. There would be a better and a weaker from each. The Better Opus would have 300 HP, 5x Mark, and very good enviromental effects while the weaker one would have 200HP, 3x Mark and weaker effect.
You could use everything against the stronger Gods and there would be a point system like this:
First God to fall: 20 points, 10 points, 7 points
Second God to fall: 30 points, 15 points, 10 points
Third God to fall: 40 points, 20 points, 14 points
But there would be strong restrictions against the weaker Gods:
You can't use Quantum Pillars/Towers and Novas/Supernovas.
You can use maximum 2 different Towers.
No restrictions for your mark.
If someone beats a God, no other player can use that 1-2 Towers that he/she used.
Points would be the same for each of the 3 Gods and it would look like this:
First kill of a God: 10 points
Second kill of a God: 12+1 points
Third kill of a God: 15+2 points
Fourth kill of a God: 19+3 points
Fifth kill of a God: 24+4 points
Sixth kill of a God: 30+5 points
Notes:
-> You get the +x points if you use a Mark which wasn't used before.
-> The same player can beat a Weaker God with two or more decks and if he/she does, he/she gets the points for all decks!
-> If someone posts a win and he/she use a Tower that was used before than he/she won't get any points.
Example
Gods:
Stronger: Opus(S), Tardis(S), Big Bang(S)
Weaker: Opus(W), Tardis(W), Big Bang(W)
Players: I,II,III,IV,V,VI
Opus(S): I,II,III,IV,V,VI -> I: 20p, II: 10p, III: 7p, IV,V&VI: 0p
Big Bang(S): III,I -> III: 30p, I: 15p
Tardis(S): V,VI,I,II -> V: 40p, VI: 20p, I: 14p, II: 0p
Tardis(W): I,II,IV,I,IV,III
Player (Used Towers, Mark): Points
I (Light+Air, Life Mark): 10p
II (Fire+Death, Earth Mark): 13p
IV (Aether, Time Mark): 17p
I (Entropy+Darkness, Life Mark): 19p (No extra 3 points because Life Mark isn't a new one.)
IV (Death+Water, Aether Mark): 0p (Death Towers were before, he won't even get the extra 4 points for the new Mark (Aether).)
III (Gravity+Earth, Time Mark): 30p (No extra 5 points because Time Mark isn't a new one. Earth Towers aren't a problem, there was an Earth Mark before, but that's not count.)
Maybe it sounds a bit difficult but imo it would be a more interesting system. You have the motivation to beat every God 5-6 or more times with different decks. That's real challenging and this way the challenge can deal with ~20 players. On Thursday, the first Realm starts. Than, on Saturday the second Realm starts. That's a total of 12 Gods, but for Chris, it's easier since there are 6+6 Gods, and the second 6 are almost the same.