Doesn't that kinda take out the fun of the arranging contest? I think it could lead to situations where the arranging-deprived person is unsatisfied with the end result.
I think the best solution for that version of Olimar12345's idea is for both members of each pair to send ideas to their partner and their partner to make the arrangement.
For example, this would be valid:
Wah and Levi are paired.
Wah assigns the idea "Waltz version of at least two Mega Man themes" to Levi.
Levi assigns the idea "Fugue on the Heavy Lobster theme" to Wah.
Wah has to make a remix that fits Levi's idea.
Levi has to make a remix that fits Wah's idea.
This wouldn't:
Dekka and Latios212 are paired.
Dekka assigns the idea "Credits version of 'To Zanarkand'" to Latios212.
Latios212 doesn't assign an idea to anyone but has to make a remix that fits Dekka's idea.