I like the idea of a Digital dash but at a reasonable cost, I just fear you would struggle to satisfy everyone's taste. I did ponder the idea of doing one myself, seen as neither of my GT4's have ODB output would be a challenge and good if I could get it right. Problem is I could see me only getting so far and no doubt would be half a job.
For the moment in the 165 I have plumped for an Acewell unit, after finding my temp gauge is buggered. I hate the thought of gauges all over the show can look very untidy. Would be nice to replace the rev counter in the 165 with a screen to do away with the some what unreliable Temp, Oil pressure, Fuel gauge and boost gauge. Dont think a circular screen is financially available this said.
To be fair the Acewell has a few little features like average speed, lap timers, adjustable temperature warning and even a rudimentary gear indicator that you program to rev,s and speed for forward and an input for reverse not that that is of much use im sure most of us know what gear we are in. Oh and it has an ODO on to make it road legal replacement.
Would like to see what you evolve from your ideas, may be interested.