You're right, there's no easy way of tying one identity of an airframe to another, registration changes are particularly difficult. Even airframe serial may not be much help; Boeing's format is OK for identifying a given airframe out of all those in our DB, but Airbus' MSNs are worse, and pretty much everyone else's worse still.
I'll need to think about this one, but being able to search previous identities by MSN and reg then copy the details might be a start.
My friend and I applied for airline jobs in Australia, but they didn't Qantas.