A simple solution for an A1200 gfx card is just to use/reuse the available Picasso design and adapt it to the A1200. This has the advantage that is a proven design with working drivers which have been already done.
The hard part is adapting the Zorro II design to the A1200 card expansion. I believe Kipper2K has bought these conectors, so it is a matter of building a passthru and buffering the required Zorro II signals at the cards interface.
Here is the link to the Picasso remake (sorry in German...):
You can take a look at this page in english with pictures taken by Matthias Heinrichs aka Matze and originally posted into his own thread at a1k.org:
A new card design will take ages to be implemented, and that is not counting driver development. So why reinvent the wheel?