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I'll vote for Slowbro, although I think Excadrill and Azumarill could also work. Slowbro plugs up our physical side, but we'll need to be very careful to cover the special attackers that threaten this team with our last two slots.
TWave Slowbro - idk whether this project is still running or not, but I think it's a great idea and we should try and see it through to the end :)
EDIT: Looks I already voted, but I'll amend my vote to TWave Slowbro