It may be a different way of rendering, but I don't think there would be any benefit, and in fact may be detrimental. It's a lot quicker to assign a color value to an array element (if pixel level manipulation is required) than to assign multiple values to a rectangle object. There are other reasons to avoid this approach, but in the end, you want to work with the API, not against, or around it.
As BurntPizza said, if performance is your top concern, consider a different API than Java2D. Personally, I haven't hit the wall with Java2D yet. I get around 1200+ FPS on a fairly modern machine at 1024x768 resolution with every pixel being touched during my rendering loop. Even my craptastic 7 year old laptop with integrated Intel video still manages to crank out 120 FPS in the same scenario. The only sure way to know is to try out a few different approaches, and see what works best for you.
Do you mind sharing your approach, it would be greatly appreciated. I've hit a huge wall and I'm sure there's something else I could do without having to move onto other API's. I would love to get that kind of performance at that resolution, but as soon as I start rendering a couple hundred images, the FPS starts sinking dramatically.