WOULDN'T it be easier if the word "the" was just simply a letter?
Well at least one person seems to think so. Aussie restaurateur, Paul Mathis has invented a new letter of the alphabet to replace the word "the" because he thinks it is more efficient. The letter looks like the Cyrillic letter 'Ћ'. If an upper case T and a lower case h were to have a typographic baby, this is what it would look like.
This will never happen because it makes too much sense.
One of the great legacies of Greece is to perfect the alphabetic system. If you were going to introduce a letter for the it would be to revive the old English ð. This was lost to the English language because the first printers in England learnt their trade in the Netherlands and when they set up presses in England they couldn't bother to have a new letter cut. Some use "y" as a substitute. Hence the spelling of "the" as "ye" is not the result of medieval pronunciation but of early modern printing.
And if you were going to reintroduce ð it would make sense to also use θ for the unvoiced form.
Hence breath would be breaθ and breathe breað.
Having said all that there are far more serious divergences from the alphabetic principle that are a far higher priority than the <th> sound. Spelling breath as we actually say it as breth to name but one.
Having single letter for "the" would be a step towards a syllabary. Do we really want to go back to Linear B?