>>42277182rip me. didn't read abilities.
regardless, I don't think that you could just force a Vaporeon into being an oversized water balloon. When a Vaporeon swims through the water, it doesn't just start sucking up water. This implies that increasing in volume is a voluntary thing.
Unless there is evidence otherwise, I can rest easy knowing that the only way you wind up with these weird inflated Vaporeons is if they consent.