When you sand blast all the protective dirt, paint, oil and crap off your frame, sure it is etched. But, what is stopping the humidity in the air from starting rust as soon as you are finished blasting. Etching primer contains phosphoric acid with converts any surface rust to a harmless inert stuff.
I'd go ahead and use the etching primer, and the other primers you have. There is nothing wrong with what you plan on doing. Different parts of the Continent quite often require some different techniques.