I'm currently considering doing a monotype run myself after recently finishing E15.
I love playing with staller/annoyer pokemon (not a fan of sweep), thus in main game my team was the likes of venusaur, cofagrigus, dusclops, wobbuffet, drifblim, lanturn, rotom, venomoth, amoonguss, jumpluff.
Since you're experienced with monotype run, can you suggest which type is most fun with a stall/annoy playstyle?
I'm thinking poison and ghost, but sadly ghost can't be obtained until 4th gym probably.
Grass seems fun, but my previous team already consists venusaur, jumpluff, amoonguss, so my next run will likely be lacking in novelty.
Any suggestion?