Hiya Jens,
A few ideas for your next (or next next) IndivisionAGA
Secure mounting:
To fix the 'wobble' you could use those silly HD cradle holes which are just waiting to have something stuck into them.
Better output:
Have you seen the graphics filters used by Mame/Scummvm/DosBox/WinUAE to enhance old VGA screens up to more modern displays standards?
Why not take the Amiga's native signal (eg 320x200 8bit) and the perform some realtime post-processing to bump it up to say 1024x768 32bit with a higher refresh. The good thing about this approach is that the Amiga would remain 100% compatible but everything would look much better