I would say that semantically upside-down-fu would be as distinct and useful - even in plain text - as the average Enclosed Ideograph, and more so than all the z-variants of rightside-up-fu ... and probably more useful than the last many thousand encoded characters.
The problem is not the upside-downness, it is that traditionally this character is *not* used within text at all, but rather posted on doors or walls. As such it has a vast variety of "presentation forms", which may be sampled via image search on "upside down fu". I don't see any way down that decorative path after assigning it just one codepoint. Fu (Good Fortune) on you, and 恭禧發財 , Zhou
