A command where pvp can occur between only two players? (idea)

[JumboCracky]

There can also be a restriction where two players also have to be 200 blocks WITHIN range in order for one of them to request a fight. If out of range, the player will not be able to send the request to the specified player at all. Normally, if two players are doing certain activities and they're unaware that they're close to each other, it's rare for both of them to suddenly burst into the enthusiasm to pvp, right?

If they chose wherever they wanted to pvp, that would be convenient. If that destroys the purpose of the pvp arena that was built, maybe it could be a VIP-exclusive thing or a perk.