For EU VAT, the only thing you need is a declaration showing it has been paid in the past. No re-registration, change of ownership
etc. changes that. So, no problems there as long as you don't loose the invoice or whatever paper you get with the boat.
About difficult offshore
registrations: yes, I think the best option is Panama and we are seriously considering changing to that now that we are there. I also think it's cost-effective but will find out in the process.
About embassies helping out... they don't. They care too much about how the local government
thinks about them; it would hurt future negotiations on economic matters. Also, they will not interfere in local prosecution / laws etc. And the officials in these countries know that. They laugh at you, humiliate you and even spit you in the face if they want. I you say something back, they seize your boat. I know all that happened to US cruisers in Venezuela
and the embassy was silent... it's even empty now as they sent the US ambassador home!
The protection you get is the lawyer you are going to hire so better hire a good one. Your only hope is that the judge involved does not consider your passport a factor and I believe most judges will be okay in that aspect.