It sounds reasonable to me too, but I don't see how having a "constitutional monarchy" is necessary in order to make this sort of thing possible. Many corporations (which are not constitutional monarchies) have policies that enable employees to take leaves of absence. The U.S. government (which is also not a constitutional monarchy) also has policies that allow judges, members of Congress, or even the president to take a break from their duties (for example, under circumstances of illness).
They have explicit policies to enable them to do that. What Jimbo is saying is that we can do it without an explicit policy. We could make a policy, but it's not really worth it.