The only way I would agree with giving any kind of reward in low level arenas is by making them have an environment effect similar to the
Journey to the North effect that modifies the stats of those that enter, making all of them equal, and allowing ALL characters to enter, regardless of level.
Level wont matter since you'll be moved to level 10 (Ascalon, Shing Jea, Kamadan) or 15 (Shiverpeaks Arena) when entering them.
They would be true low-level arenas, without advantages.
Unless such an effect is added to the 4 low-level arenas, absolutely no kind of reward should be received in them, not even the Balthazar and Exp players may already get.