my other gym would be a ghost gym. the 8th gym.
my team:

Lv. 47 Hypnosis, nightmare, dream eater, toxic

Lv. 49 Calm Mind, toxic, gravity, earthquake

Lv. 48 ice shard, hail, ominous wind, confuse ray

Lv.50 power gem, mean look, perish song, lucky chant

Lv. 47 embargo, shadow ball, shadow claw, dark pulse
the puzzle would be a maze with trainers lurking at every turn, where beating them makes the light brighter. (like bradley's gym only much bigger)