Audi D2 FL instrument cluster
 

Here is one project with final design for instrument cluster for D2. Is used C5 cluster fitted to D2.
https://i.imgur.com/6Upw1cK.jpg

Nice! Thats C5 cluster internals in a D2 cluster housing?

Do all the buttons still work? Does the fuel gauge behave properly?

What are the main benefits of doing this?
I can see that you lose the colour display, but gain the voltage gauge

and oil temp gauge. So annoying that the D2 measures oil temp but won't show you it.

Fuel gauge is need to be reprogaming eeprom to work properly. On C5 work on backwark. And with different resistent from sensor.

А6 internals with new custom face to D2 housing.

Main benefits is ABS 5.7 and D2 have modern brakes. But this is other modification.

I wonder if that would allow 'proper' RNS-E directions on the DIS? I expect it should, given the RNS-E was available in very late C5s

This car not have RNS-E, so cant confirm.

Same with the battery gauge. Why do manufacturers remove the useful dials all the time.

Main reason is not for extra gauges, but very good upgrade for ABS and brakes. D2 not have good brake at all, which is caused by bad ABS system.