In that case, it makes maybe more sense to create tools for this, e.g.
- the editor provides autocomplete which maps Unicode names to the corresponding characters, e.g. when I start typing “ZERO WIDTH…”, a drop down menu suggests that character,
- a built tool (preprocessor) which converts the
&"NAME"; syntax into the corresponding character.
Even if, say, Chrome and Firefox, implemented support for your proposed syntax, authors would still have to provide fallbacks, and in this case, a preprocessor would be a good option (a better option than a JS library which dynamically replaces this syntax on a live page). So why not just leave it at a preprocessor?