I really think this is a cool idea, and I bet you can pull it off, but I only have one problem with it.
With what you said, it sounds like the rest of the game is going to stay as normal fire red, and the only thing that will change is after you beat the elite four, you go to orange islands.
That's nice and all but that's only like 10-20% of game play compared to the rest of fire reds gameplay.
It's a cool idea and all but I myself wouldn't play through fire red just to play through only like 1-2 hours of gameplay.