I previously avoided this due to being unsure of the effects; however, it's clear that we already use typed properties on Threaded things in other places anyway, and the only known issues are with uninit properties, and arrays.
this gains a very small performance improvement by avoiding unnecessary !== null checks on every packet written in either direction. It's insignificant for sure, but I just found this code in an old stash, so what the heck.
at this point it's really not much more than just a thread-safe way to transmit parameters from main to thread. Maybe we can ditch it in favour of a generic closure-based thread implementation.
