I have a Twiddler 2, and although the pointer drift was a pain, I did like the track point better for input than the idea of an 8 way hat. It is one of the reasons why I haven't upgraded yet.
What I would really like, and I think would work really well for everyone for pointer control, would be the integration of one of those haptic feedback circular customizable trackpads that are on the Steam Controllers and HTC Vive hand tracking remotes. I think they work wonderfully for mouse input (as well as other things). They are comfortable for the thumb, don't seem to drift, click for button input, and have reprogrammable touch zones, It would offer so many options for customizing input to suit just about anyone's needs. The steam controller is a interesting little beast and takes awhile to get used to for gaming purposes, but for pointer control the dished circular pads work just wonderfully and are light years better than the old trackpoints.
While you are at it, an accelerometer for basic gesture tracking would be wonderful too. I have a simple keyboard remote with an accelerometer in it for Home Theater PC use and works great. The gyro in the Steam controller also can be used for precision pointer control as well.
With VR uses on the rise a future Twiddler would benefit greatly from these features.