Thanks for all the comments!
STOKIE & Wassy are on the right track.
I was hoping someone has already reverse-engineered the diagnostic messages on the kawasaki, so I won't need to do it myself, as it takes a fair amount of time.
I've found a similar project that someone undertook for a Harley (http://momex.cat/en/tachometerHD
) , which will be a good starting point for me.
In short, They added a DIY tachometer & gear indicator (see http://momex.cat/images/tachohead.png
What I have in mind is a bit more advanced cluster, with ambient temperature, accelerometer, internal temperatures, maybe fuel consumption, gear position, shift light, GPS directions, front & rear onboard cameras and some additional bits & pieces... not sure yet if I would want this displayed on the phone or I would rather have a separate purpose-made screen.
The way I see it end result would be similar to a track datalogger (i.e. here's a random one from the internet https://www.aimshop.com/products/aim-evo4s-motorcycle-racing-datalogger
) ... though it would be more adjusted to daily driving needs.
With all this feature list, of course it would be a long-term process of constant prototyping (gotta love 3d-printers!), but In the end this is something I would like to fit in my future bikes, hence why the question was about all generations of versys (current bikes communication protocols are a bit more standard, so at some point this dashboard would be plug&play across any motorbike, or a car for that matter)