I've finished my day job and go back to design table. I've managed to finish the back case today, so the project design time it's almost done.
I've added the lipo charger (powerboost 1000C), an on/off switch and the audio amplifier in the back case. Also, there is some room for 2 3000 mAh batteries. (assuming a 1.5A current, it will be 4 hours of awesome retro gaming)
The main things to do know it's to create shoulder buttons, created a way to anchor the screen to the frame (I'm thinking about something already) and create some holes in the back case to hide the m3 screws that will hold everything together.