Few comments:
1) The default policy for create functions is epmfs not mfs. So you might not get the behavior you expect.
2) defaults,allow_other,use_ino,hard_remove... defaults and hard_remove are both unnecessary (though harmless). You can see the official docs for a suggested default. In a future release use_ino will also be unnecessary.
3) Using the package from your distro is going to give you a reasonably outdated version. You can find packages I built of the latest releases on the github releases page.
Yes, I've considered a PPA but auto updating software like mergerfs that can break a system if I screw up and introduce a bug is not something I really want to take responsibility for. I could keep it a bit out of date I guess to help lessen the likelihood.