Another experiment/suggestion.
I rewrote get_i using variadic template:

template <typename A, typename... T>
constexpr A get_i(int i, const A& p0, const T& ...args)
{
	A list[] = {p0, args...};
	int n = sizeof...(args);
	return list[clamp(i, 0, n)];
}

const char* cr = get_i(1, "zero", "one", "two");
RDUMP(cr);
int ir = get_i(1, 0, 1, 2);
RDUMP(ir);

IMHO, my implementation is much shorter and it will compile faster.
IMHO, macroses __List and __Expand are not needed anymore ...