I'm using this proposal in my systems:
https://github.com/darconeous/ham-addr/blob/master/ham-addr.txt.md
Maybe it is useful to develop a simple tool, e.g. a webpage with some javascript, that allows input of a callsign in a field and converts the input to the HAM-64, EUI-48 and EUI-64 forms as far as possible. A similar tool could work the other way around. This allows some experimentation.
Rob