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Lots more than 26, in fact, so presuming someone could find a set of 26 typefaces such that each one of those typefaces could be readily distinguished from all the others in that set on the basis of a single character...
instead of saving ink and paper with such minor steps like having really short descenders and huge x-heights, each letter could now encode the letter following it in its typeface, thus cutting the length of texts almost in half!
I'm assuming that for readability, words would still be separated with spaces, and so one might have a 27th neutral typeface for the last letter of words with an odd number of letters.