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Fencer: Hmmm, that's a tough call! I would imagine it would be less of a hassle to enable players to choose their own start positions on the games already going. Although, the possibility of having players create their own variants would be super cool.
But I think it matters the cost of it. And if both setups cost about the same, then I'd choose the creation of variants.
It would certainly be something no other game site has!