I really enjoyed playing down in arena 1 to test different formations and personnel without fear of losing stars due to a loss. I feel like it really encouraged creativity; whereas, now I feel like I'm kind of stuck using what's been working or else I'll tank fast. I think implementing some sort of "practice arena" would be a huge help, especially for lower players who are just unlocking formations and players.
To clarify, love playing where you're meant to be playing but definitely feel there is a need for an area to test out things without fear of being relegated. Maybe have no rewards for wins in this area?