It seems my buss-mans holiday paid off this time. Within two hours of hitting the code again, I discovered that although the LOAD OBJECT command was gobbling a little more memory than it should, the real villain of the piece was LOAD IMAGE which had been placing MOST of the texture content in system memory as a managed backup. My building ate 23MB in the old Image DLL, but with some extra code to ensure certain commands could still lock a video memory texture, my new Image DLL loaded the same building in at 9MB. Multiply this effect by an entire level and you will start to appreciate how this single tweak has improved your lives in Reloaded land :)
My investigations also saw the LOAD OBJECT memory usage double when the LOAD EFFECT applied it's magic to it, so there is something very suspicious happening there too. Going to stop my weekend work for how, and celebrate my code win with some good, and Sunday/Monday I will chase down the reason for the shader taking my 3MB model up to 6MB (and then find out why my model was 3MB in the first place given that the vertex data cannot be more than 1MB).
In order to think laterally, you need to approach a problem for an entirely new direction. Leaving your code for a week, then returning to it is one way to do that, and leaving it to talk geek for a week is probably the best way to prepare your brain for the comeback.