Hope i'm not too late to answer
I have this interest towards pathogens which perfectly cimbines with my love for poison types.
My gym would be in a laboratory. Before getting to the final GL battle the trainer wil have to battle with the interns. Each one poses a micro-related question, If the answer is wrong, battle conditions will get harder (Each trainer is studying a pathogen and the field effect will vary accordingly):
-First trainer is studying Salmonella, the player will have three test tubes in front of him and will have to detect the one containing it. If the quest misses, every one of his pokemon becomes infected (except steel types) and loses hp each Turn because of body water loss. Effect is worse If sunny day is used
-second trainer awaits before a CL. botulinum petri plate, trainer will have to press a button to change pH of the solution to inactivate it. If it misses, his whole team will be paralyzed.
-third trainer has some samples containining a. Niger trainer will have to recognize and avoid the contaminated sample otherwise all his pokemon become affected by the toxin which can outburst at any point during battle causing either bad poisoning or fainting (according to pokemon hp and def stats)
-last comes the gym leader who's studying s.aureus. and l. Monocytogenes. trainer will have to raise the field temperature to a safe level (prior to battle), otherwise They will form a biofilm which reduces the speed stats of trainer's team and when a physical attack misses They can be either poisoned or confused. Steel types are not immune since these bacteria can grow on it.
Each trainer of corse will provide the trainer with necessary hints on how to solve the following quest, giving a hidden tip on how to sirvive If worst comes.
My team would be : drapion, roserade, toxicroak, Crobat, muk and dragalge.
I know i'm a bit weird but i swear i'm not dangerous