Hmm, never thought about this actually. Mostly cause I've always looked forward to beating all of them instead of thinking about how things would be done if I was one. I'd have Psychic types, since they're my favorite ones in all 4 gens. Of course, since Ghosts can use Psychic too...
There's no traps anywhere in the gym, it's just set up so that you have to fight every one of the trainers before fighting me. You're able to see the room I'm in as soon as you enter the gym, but you can't get in without opening the locks on the door, and you must beat a trainer to get a key to the door. You have to beat them all to get access, and since all of them will be strong enough to give me more than a run for my money, it won't be easy. Plus, you can't leave the building for anything other than emergencies once you're in so you better bring enough potions and heals.
I'm either the 7th gym or the final, 8th one, it doesn't matter to me as long as you fight me that late on.
1. Metagross Lv. 40
2. Gardevoir Lv. 42
3. Gengar Lv. 44
4. Dusknoir Lv. 46
5. Gallade Lv. 48
6. Alakazam Lv. 50