I also wonder why there's so few experimental keyboards with any kind of built-in mouse. Realistically you need one and I feel like switching one hand between the keyboard and mouse should be optimized as well. At the moment I'm using a 65% keyboard and a Logitech track ball next to it. I'm mostly happy, but I also feel it could be improved. The ThinkPad TrackPoint keyboard is probably the best solution I've found so far. In prehistoric times I've tried the TouchStream but that just didn't click for me.