I know that Brendan/Noah (forget which one) joked about Gladio being "another season" of Blowback in one of the episodes of Blowback S2, but I am curious what people would be most interested in.

I do think that a season focusing on Europe (either Italy and the Years of Lead specifically, or US covert operations in Western Europe more broadly) would be a good topic. Afghanistan would be very topical (specifically the rise, fall and rise again of the Taliban), but might be a bit close in content to their season on the Iraq War. I'd also be really interested in a season focusing on an African topic, such as the Congo, or the French/US operations in West Africa.