Using an iPad with an external keyboard is an interesting experience. There are often times where you need to reach up to the screen to accomplish a task because there isn’t a keyboard shortcut or a pointing device to assist you with that task. Dragging and dropping things can be frustrating as you’ll need to take your hand off the keyboard to do it. Selecting large amounts of text and moving it without reaching your hand up to the screen is almost impossible. This is unnecessary friction that could be solved if Apple allowed the iPad to use a trackpad.
Perhaps I am in the minority but I just don’t see the need for a trackpad. This would need to be multitouch and incorporate a multitude of gestures for multi tasking. If you’re going to the extent of adding on a surface style keyboard and trackpad I would say three words.
Buy a MacBook.