Presumably, with the “u” indicating the corresponding semivowel /w/.
Great link. It says Esta aspiración aún se conserva como rasgo dialectal en Andalucía, Extremadura, Canarias y otras zonas de España y América., which I understand as “This aspiration is still preserved as a dialectal feature in Andalusia, Extremadura, the Canaries and other areas of Spain and America.” In other words, Spanish h is still around, like -gh- in English (cf. Scots English nicht, licht).
That change isn’t all that unusual. In Irish (=Irish Gaelic) and Scottish Gaelic, initial F regularly changed to H in certain grammatical environments, and like Spanish that change is now between F and silence (spelled “fh”) except in a few words.
Well, yes. It mentions that occasionally, in some dialects, the h, especially if combined with other vowels, can stand in for some slight sounds (exact phoneme varies with vowel combination).
Exactly. But it goes beyond that. There are quite a few dialects alive inside of Spain – such as Bable*, which I semi-speak & understand due to blood-lines – and many others variations of Castellano Puro outside of Spain that keep some of these sounds as DiggitCamara touched on in his post.
In short, for quite a few number of rational reasons, the Spanish “H” be it strictly orthographical or for sound reasons, is here to stay.
*Facer = hacer. And again, many many more.
One somewhat archaic spelling that has persisted is Mexico, usually pronounced as Me-hi-co, which in modern Spanish would normally be spelled Mejico. This is an artifact of Spanish orthography at the time of the Conquest (also seen in Don Quixote). In modern Spanish “x” is usually pronounced as “ks” like in English (although sometimes pronounced as “s” in some regions).
Don’t forget the historical impact of printing presses and widespread literacy (and, sometimes, nation-state consolidation) when trying to explain why spelling conventions, in just about any language, tend to be more or less “frozen” at a pretty specific time period. Indistinguishible, that explains your “hacienda,” etc.
Woops, wrong thread.
You meant “whoops.” 
Very interesting example of parallel development, thanks Drake.
BTW, the current sounds ascribed to h + vowel combinations are not in any way the same as the f phoneme. While at some point yes, hacer perhaps sounded like facer (as* fazer* is currently the same word in Portuguese), none of the current slight sounds resemble that, and in fact, all are softer variants of the phonemes for g, j, and* y*.
In Japanese, the phoneme /h/ is a development from an earlier /f/ (and still is /f/ when followed by /u/). Both the /f/ and /h/ in their turn are developments of an archaic /p/, which is why all 3 consonant sounds are written with the same kana.
In Khalkha Mongolian as in Irish, an archaic /p/ has disappeared altogether, by a series of mutations:
p > f > h > zero
In other words, the phoneme /p/ long ago disappeared from Irish and Mongolian altogether, much as the sound /x/ (written with “gh” as in night) originally present in English has disappeared. There’s another Mongolic language which, having taken the process only partway, has preserved the phoneme /f/ or /h/ in words where it corresponds to zero in Khalkha. Modern Irish and Mongolian words with /p/ are not native to those languages but borrowed from elsewhere.
I could have sworn the reason for this spelling was rooted in native languages and the difficulties they raise when one tries to map one word from one language to the next.
However, the Real Academia de la lengua completely agrees with your post. Ignorance fought!
The same source, in the article on the letter x linked from that page, goes:
‘In the Middle Ages, the spelling x represented an unvoiced palatal fricative sound, whose pronunciation was very similar to that of the present-day English sh or French ch. Thus, words like dixo (today dijo) or *traxo *(today trajo) were pronounced [disho] or trasho] (where [sh] represents a sound like the one we make when we want to impose silence). This archaic sound is kept in Mexican Spanish and some other areas in America in words of Náhuatl origin, like *Xola *[shóla] or *mixiote *[mishióte] (not in Xochimilco, in which the *x *sounds like /s/), and in the archaizing pronunciation of certain surnames that retain their old spelling, like Ximénez or Mejía.’
Mexico was named after the Nahuatl-speaking Aztec tribe of Mexica, pronounced Meshika.
Yup. Also “Xalapa,” capital of the Mexican state of Veracruz, which is sometimes spelled “Jalapa.”
Interesting what you pointed out about Nahuatl “sh” sound being transliterated as “x” in Spanish. In modern Mexico, people usually think of the MAYAN languages as using “x” for the “sh” sound, while NAHUATL and its variants are though of as using “x” for the “ks” sound. For example, Tlaxcala, a Nahuatl-derived place name, is pronounced “tlahks-KAH-lah,” while Uxmal, a Mayan-derived place name, is pronounced “oosh-MAHL.”
But that’s not necessarily the reason the “h” is kept, is it? How would we know? Perhaps-- If there are no examples of a non-homophomic “h” being dropped, then I think we can assume the homophone isn’t a reason it was kept.
No, “wxoops”. 