I'd be content if Namco simply made the ground level textures and such more realistic, so if you fly over a city, I want that entire city modeled in 3D , tiny sprites for people and tiny cars modeled out of 10 polygons, I want to be able to fly through said city breaking the sound barrier and watch glass fly off of office buildings from the sonic boom sent rocking through the atmosphere. If I fire a missile waywardly through a populated area I want the explosion to send cars shotting into the air , maybe buildings collapsing and such.
To put it simply I want a nicely modeled destruction simulation. Even on the planes this level of destruction would be cool, make each bullet stream cause dents and debri to appear off enemy planes, a direct hit with a missile should randomly trigger a destruction sequence of some kind. So maybe if you hit the engines it goes up in a huge fireball sending blackened bits and pieces towards ground but if you hit the middle of the plane it gets visibly blown in half before it makes a huge fireball.
The same thing would apply for trees and such on mountains, in teh past you could fly right near the ground and the photorealistic illusion was lost somwhere around 800 feet in the air, it became a pixelated mess, so add more shit on the ground, maybe a layer of rendereing that appears if you get really close that isnt' there at 1000 feet, or better yet just make it so you can't get close enough to the ground to mess up the illusion if they can't get it running well enough.