Well for the touch support of the dual screen that would work, problem is hardware keys and turning them into touch controls.
- For the DS emulator you can use any stable out there like DeSmuME
- To run DS emulator on RT devices which doesn't support desktop applications head to my tutorial on how to get any desktop application to work on windows 8 RT.
I have been developing a virtual joystick for Windows tablets but somehow I can't get it to direct input into DS emulator, so instead I found a developer on XDA which doing a similar project and though to make a tutorial where you can customize the keys and use them on your own for any emulator out there.
Head here and download the virtual joystick for windows tablets.
My personal recommendation would be using a real Blutooth gamepad, or simply PS3 controller with your tablet and use the tablet screen for only the touch screen on the second screen, as you can see the below example, I am not recommending any brands just found this on image search it shows the kind of gamepads I am talking about which holds your tablet in the middle and than you can use it as a handheld console: