This would allow the mapmakers to create arena-specific maps.
For EW, no 17-pound AT guns, less (or less lethal) ack at towns and bases, smaller towns or increased down times for buildings, etc.
For MW, same kind of thing but ramped up for the better equipment available in that timeframe.
I realize some of this is adjustable in the arena settings, but apparently everything is set at default levels. Even the change in settings would go a long way to bring people back to those arenas...more people means more fights and perhaps less toolshedding or perk farming.