The lightning must be so that Sasuke gets to freebie use Kirin, a jutsu requiring no chakra of his own which noone can defend against. As seen here, Sasuke can guide lightning:
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With the potential of the EMS, combined with Kirin, might make Sasuke the most powerful ninja at this point... maybe Sasuke will interfere with the kage's vs. Madara fight. For Sasuke to battle any other opponent(s) would be ridiculous, no ninja in the manga would even be brave enough to challenge him. Also, I find Madara vs. the 5 kage to be pretty evenly balanced, Sasuke wreaking havoc is the perfect oppurtunity to resolve the stalemate.