The whole point of LATIN CAPTIAL LETTER SHARP S (U+1E9E) is that some people don't consider eszett as a pure ligature of long-s and s, but rather as something special that stemmed from that ligature.
The fact that "Maße" and "Masse" are two different words shows it's not a regular ligature like ff, fi, fl, ffi or ffl, because those don't change meaning of words, whereas ß does.
People who want to use U+1E9E, do so to avoid ambiguity. Having a double S instead, will be no use to them.
People who don't want a capital letter sharp won't be affected either way.
You might as well not fill in the codepoint.
The whole point of LATIN CAPTIAL LETTER SHARP S (U+1E9E) is that some people don't consider eszett as a pure ligature of long-s and s, but rather as something special that stemmed from that ligature.
The fact that "Maße" and "Masse" are two different words shows it's not a regular ligature like ff, fi, fl, ffi or ffl, because those don't change meaning of words, whereas ß does.
People who want to use U+1E9E, do so to avoid ambiguity. Having a double S instead, will be no use to them.
People who don't want a capital letter sharp won't be affected either way.