All your suggestions seem recommendable but this one is so obvious. In most European countries, the CAA published details per registration at one time but most or even all of that has been withdrawn - only the UK CAA stubbornly continues to offer valuable and effective information to the thieves.
I wonder why nobody is sueing them for breaches of privacy.
Probably because there is little chance of success. Today's searcheable aircraft registries are a way of complying with Article 21 of the 1944 Chicago Convention. The FAA
registry has been online for years and I would suggest that if it breached privacy laws, this would have been tested in a US court.
The French
register not only shows the owner/operator, but where the aircraft is based. However, in France most of the aircraft with Rotax engines are ULM and therfore not on the F register.