Perhaps a bit off topic (and not solving the OP's actual problem that everyone seems to have ignored, which was about sequence numbering rather than the display of footnotes themselves)...
I recently read an Oxford University Press book which tried to get around the small-tap-area problem by not only linking the footnote anchor itself but a few words previous to it. This seemed a good compromise between the standard printed approach and a reasonable digital experience. (see attached)
Regarding the use of numbers -- I've had the problem of multiple unnumbered notes in a book (* or the like), where clicking on one took me to a page of multiple notes, without any clue as to which note was the specific one I was referencing. So numbers do provide some value, even in e-books...
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