For AEW I think the E-2 would be out of Brazil's price range, and the aircraft itself might be marginal for her catapults (British BS-5s, 151ft stroke). A more suitable solution might be to acquire six or more S-2 Trackers from AMARC, convert them to S-2T Turbo Tracker standard and equip them with a palletised radar system like Cereberus (currently theoretical I know, but definitely feasible). Deploy three to four aboard ship and the rest shoreside for training/attrition replacements. As to the strike aircraft component, Sao Paolo is operating well below her capacity at present. She has room aboard to operate up to 40 Skyhawks, yet Brazil only bought about 23 aircraft. If their Skyhawks were upgraded along the lines of the New Zealand 'Kahu' aircraft with an off the shelf radar such as APG-65. Also buying up surplus stocks of Super Etendard Modernise from France as they are retired to fill out the air group, so the Skyhawks could be moved to the air defence role (with radar the possibility of AMRAAM or at least Sparrow being carried enters the game) with strike as a secondary role in support of the SEMs.
So I'd envisage an air group of 12-14 radar equipped Skyhawks, up to 18 SEMs, 4 S-2T AEW Trackers and six helos for SAR (Sea Kings, currently in service, supplemented by second hand examples from either Britain or the US). As for shipboard defence, rather than wishing for an area defence system that would break the back of the Brazilian defence budget, how about something simple, self contained and relatively inexpensive? Two RAM systems backed up by a pair of Phalanx guns, one each port and starboard.