Ram air intakes only add a little hp at very high speeds. I remember seing some things about it on sport bikes years ago. I think it only added 10 jp or so on a 150 hp engine at speeds over 150 mph.
A true ram air intake is also getting air pushed into it at the front of the bike, not behind the radiator, where it will be drawing hot air.
Even if you designed a ram air intake that actually pressurized the airbox somehow, it would probably play havoc on your jetting and overall carb operation, as the carb is designed to operate on a specific vacuum and pressure drop to meter the fuel.
I personally think its not something id spend my time on on a zilla.
Now, the aluminum airbox, id love to.see. Im interested in seeing what you come up with.  Id like to have one for my quad, maybe big enough to hold and remove a larger filter and have an outerwares filter top cover on it.  Looking forward to seeing your idea! You should post pics and or measurements if other members wanna try to make one. The stock airbox sucks.