Even better, let's just add more pop ups in the game that pop up when you enter an empty grind zone and gives you the option to select "spot taken".

Now a giant steel wall falls from the sky that encompasses the whole rotation with flashing neon signs displaying "Spot Taken".  Anyone who attempts to climb the wall is immediately frozen and spammed with "This Cutscene Can Not Be Skipped" and instantly flagged for pvp. The owner of the spot will get another pop up in which they must accept regardless of buffs they have running and must now fight for the spot.