Haiku definitely contains some interesting ideas. But rather than building a whole new operating system (even an open source reimplementation of a long discontinued proprietary one), might it make more sense to take the innovative features of BeOS, and add them to an existing OS (e.g. Linux)? For example, that file system attribute feature sure is interesting, but does it need a whole new OS? Couldn't you just create a new filesystem, say for Linux, to provide the same function? (maybe use the existing xattrs concept in Linux, but maybe add some IOCTLs to enable fast querying for xattr values?)
If you are just doing it for fun, then hope you have fun! But if your hope is that someone else finds what you produce useful, it might make more sense to extend an existing system than build a whole new one - uptake is more likely that way.