How about internal ceramic coating as a barrier against galvanic corrosion?
If it's tough enough to survive inside the engine or exhaust pipes, the
coolant system should be a walk in the park by comparison.  A quick google
search pulled up these guys
http://www.classiccoatings.com/ceramic.html#internal.   Seriously though, I
think we are looking for things to obsess about at this point.  I will
change my coolant every couple years and hope for the best.

Jay Brown

'85 Zetec Westfalia

'87 Zetec Wolfsburg