Homebrew could already get access to paths by using different nodes. FSHax allows games to access paths that they would otherwise not be able to. For example, let's say a legit copy of Mario Kart can't use the SD, so if SDCaffiine (which loads mods from SD instead of the original path) steps in and tries to tell Mario Kart to read the file from SD instead of it's own directory, Mario Kart can't read the file, and it crashes. With FSHax, SDCaffiine redirects the path and Mario Kart reads the file.
So it's helpful in that regard, but it doesn't get us any closer to changing the boot process.