On the topic of blazers, I have recently seen a vintage Sportex number in navy that looked indestructible. The downside, said the owner, was that it attracted dust easily. That drew me to the idea of a mid weight navy blazer that can take a lot of abuse.
Is Tweed the best option here? I am currently looking at all smoother Tweeds in the 13-16oz range, what does everybody think? I don't want something that looks too country.
Do you literally mean blazer, i.e. a navy coat with metal buttons? If so, best option is usually some form of serge. LBD Oyster is a good heavyweight. Fox do a couple, but I've not seem them made up.
For something with a bit more texture a hopsack can be good - I really like Dugdale 9428 from the Town Classics bunch. Or some 15oz Fresco....