I must admit that I'm puzzled that you keep suggesting that Brazil isn't "iconic" enough as a country to be represented at World Showcase... yet Portugal is?
Surely if you think about Brazil you immediately think of Christ the Redeemer, caipirinhas, Carnival, soccer, samba, carnival, beaches, the Amazon, etc, etc? It's not like they're proposing, say, a Surinam pavilion that might leave people drawing a blank regarding what to expect.
When I think of Brazil, I think of Christ the Redeemer, and the beach. There are beaches in many countries, even the ones in Epcot now, which are not represented. Soccer is popular in most European countries as well, I'm Italian, so I would associate soccer with Italy amongst many other European counties, but it's not represented in any of their pavilions. If we are going to use samba as an idea, then why aren't we suggesting flamenco in Spain. I don't think it's really valid, every culture has iconic dance styles.
As for Carnival, I'll agree with you that it's iconic, but again, every culture has parades, festas, fiestas, celebrations, etc that are not really represented in their pavilions. (except Mexico's day of the dead).
I meant in terms of architectural aspects, as they would have to build a physical setting. I doubt they would create the Amazon in Epcot, as they already have AK. It would be sort of odd to have a jungle amongst iconic architectural structures in the other pavilions, or a beach.
When I think of Brazil, I also think of Portugal, due to it's origins lol. I'm not saying they should never make a Brazil pavilion, but It wouldn't be my first choice. I just gave a pictorial list of iconic monuments in Portugal. It's also iconic for it's Age of Discovery. Visually, the Manueline architectural style cannot be compared to anywhere else in the world, as it only exists in Portugal. It's also famous for having a large impact on the Romantic period of architecture.
If you read my other posts, I also suggested Spain, India, Egypt, and Thailand, which are all far more iconic than Brazil IMO. I'm from neither of these places, so I don't have a bias. Anything new would be exciting.. even Brazil lol.