You can't compare the Miata chassis to the FT86 because well, its entirely a different style of chassis using completely different components:
Not to mention the Miata lacks a roof and are not that cheap anymore.
Cars from the 90's also used significantly LESS steel than modern cars. Less bracing, simpler chassis, smaller cars. The reason why I'm using the early Imprezas is because their size and drivetrain is similar enough for a comparison. Later model Imprezas have significantly larger, beefier chassis that weighs a bit more making the comparison much more difficult.
An aluminum hood versus a non aluminum hood only does not save that much weight. I have an aluminum hood on my Impreza for example, it only saved about 25lbs.
Aluminum is also EXPENSIVE compared to steel, so if Toyota/Subaru DID use a lot of aluminum on this car, it would make it significantly more expensive. They have stated the hood and possibly the trunk might be aluminum, but this is not unusual for Subaru's anyway.
The Veloster is light because it is FWD. If it were RWD, it would weigh another 200lbs at least, even heavier than the FRS/BRZ.
The point of this thread is to show that the materials and components used on this car dictating the weight of the vehicle. In no way is it exact method, and to be honest it doesn't really matter that much. I just wanted to give people an honest assessment of why this car WON'T be a super-light weight.