As can be seen from the "translation" table on the Wikipedia page you linked, there are multiple alternative glyphs associated with every letter, most of them composed of multiple letters themselves.
No simple replacement font is going to be able to display \_:_/
in place of a w, as it is five characters.
Why couldn't a w be much wider, and consist of 5 characters copied from a different font. I don't see any
technical reasons why this couldn't be done. It'd be an annoying job, but don't see why it couldn't be done. Of course you'll have a single glyph per character, but it could easily look like multiple characters as far as I can tell.