Similar disclaimers as usual about not commenting on possible or actual features, I will say this: our integration of anything which isn't an open service/open standards/is a brand is going to require communication, agreements and contracts with the people behind it. So using WhatsApp as an example, it wouldn't *just* be based about the technical possibilities as to whether or not we could include such a thing, even assuming we can polish the experience to a world class standard. They would also need to be OK with us doing that, on whatever terms they dictated.

That having been said: I don't think anyone would stop you from messing with something like this yourself. Quite the opposite.