Months ago, I published, on Flags Forum, a draft for a new coat of arms of Brazil that, different of the current one, follow the heraldic practice. After some corrections and additional research, I present it to you.
The current "coat of arms":
My proposal coat of arms have some additional concepts: it's inspired by the CoA of Guyana, maybe the best in South America; while the dexter (the left side of the viewer) will have elements related strictly to Brazil, the sinister (the right side of the viewer) is related to elements inspired by Brazilian colonial past.>
From this point, I think I can present my proposal:
[click on image to enlarge]
The shield is a composition of the arms of the Kingdom of Brazil (the armillary sphere being later used by other Portuguese colonies, and by Portugal itself) with four white stars in cross, representing the Southern Cross. White stars on blue can represent a large symbology related to Brazil: the naval jack, the current coat of arms, the Order of Southern Cross in its imperial and republican versions, etc.
The coffee and tobacco branches are used in both the imperial and current coat of arms. The red lace can remember the etymology of Brasil: "of flame-color". The supporter of the dexter in a jaguar (Panthera onca), the biggest feline of the American continent (and the third of the world, after the tiger and the lion), present, for example, in the 50 reais banknote, holding a banner made of a simplified version of Brazilian flag. The sinister supporter is a green wyvern, that was used, in Portugal, as a symbol of the house of Braganza. The first emperor of Brazil, himself a member of the cited house, used golden wyverns as supporters of his arms (and in his self-named order). The dragon is holding a banner of the Order of Christ, that's generally regarded as the "first" flag of Brazil (see official timeline, in Portuguese).
The helmet and the wreath are green and yellow, the main national colors of Brazil. The crest is an indigene headdress. I didn't use any motto, because Brazil officially don't have one: the empire used Independência ou Morte ("Independence or Death"), the current flag have the Positivist-inspired writing Ordem e Progresso ("Order and Progress") often considered politically un-neutral, while the current "coat of arms" have a simple República Federativa do Brasil ("Federative Republic of Brazil") as motto.
Although I see a heraldically-correct national coat of arms as a nice idea, I don't see any problem in keeping the current arms as, for example, "presidential insignia" for historical reasons.
This is only a concept, therefore your comments, suggestions, etc. are welcome.
If you're not familiarized with basic heraldic vocabulary, this can be useful.