I do feel sympathy for the good folks in Australia who enjoy shooting black powder, muzzle loading firearms. Aussies are among my favorite friends, to be sure. But you are living in a more restricted nation than many others, especially where firearms are considered.
I do not know all of your regulations for ML's, but am gradually learning a few of them.
A few years back, I considered re-locating to your wonderful nation, but was put off by the very restrictive firearms rules/regulations.
I do wish you the best in creating your ML, and hope that you are able to build something to your liking. If I can help in any way, please let me know.