As much as I love the flavour I don´t see Aromatisse improving with Poison subtype so that is out for me.
No Guard Hypnosis sounds fun, but Poliwrath would still be in the miserable situation to decide between "bulky" and "offensive" sets.
I really want to vote for the cutest Bulldog, just because I love them, but the actual vote goes to...
Protean Hydreigon
I would expect him to make an impact on bulky offense as a stall breaker but also as an occasional Tailwind setter to overcome Hyperoffence, it´s quite a momentum machine.