except the GEMS dash units cost fucking £3k for a semi reasonable sized TFT unit!!!!
Not at all, the LDS 4 that all the single seaters and the WRC use come it at sub £2k for a proven unit.
When you are talking that kind of money, you are better off buying an off the shelf hardened PC based car computer, and paying someone to set it up so the dash page of the M-TECH ecu comes on automatically on ignition start up etc.
Looked at that, and couldn't find anyone who wanted to do it for me.
And i could have much much bigger than a puny 5.7" TFT!!!
Yes because you want a fucking 34" LCD/Plasma displaying the vehicle parameters at you when your driving at night 
It just needs the software package to be intelligently written - most mapping software or ECU interface software has a basic "dash page" just make said page more customisable, or have a cut down version of the software just for the dash.
total user interface on all GEMS unit now, as with most of the other PROPER units out there. Not your micky mouse shit.
Hell look at most high and mid range cars now, full TFT dashes with digital dials the lot run through canbus from the ecu. Background just needs to be a bitmap which can make it look fancy as hell when in reality it isnt necessarily so fancy in implementation (nor does it need to be).