Another thing to consider: Tuple is moveable if all its components are moveable. Are we able to express that somehow? (If not, no big deal, I can make Tuple moveable and request that elements are).

struct not_moveable {};

template <class A, class B>
class Two : std::conditional<is_moveable<A> && is_moveable<B>, moveable<Two<A, B>>, not_moveable>::type {
	A a;
	B b;
};