In fact, that has happened long before the capital letter sharp s was added to Unicode: The T1 encoding (aka Cork encoding) of LaTeX
does this since 1990. The reason for this was correct hyphenation for German words rendered in all caps.
--Jörg Knappen
Gesendet: Samstag, 01. Juli 2017 um 08:51 Uhr
Von: "a.lukyanov via Unicode" <unicode@unicode.org>
An: unicode@unicode.org
Betreff: Re: LATIN CAPITAL LETTER SHARP S officially recognized
Is it possible to design fonts that will render ẞ as SS?
So we could choose between ẞ and SS by just selecting the proper font,
without changing the text itself.
Or perhaps there will be a "font feature" to select this rendering
within the same font.