The biggest problem with Gorky17 on A1200 is memory requirements and slow BlizzardPPC/Mediator combination. At some point this might change, if/when improved R200 drivers are released. I am going to do so tests for Daniel MuBener on my A1200 soon. So let's wait and see :)
What happens if you only disable voodoo3.chip and keep pcigraphics enabled. make sure you have NO Elbox drivers running then otherwise they will interfere.
Its important when you report problems that we know EXACTLY what is going on. and that no other 3rd party drivers interfere.
If for example disabling voodoo3 already makes the system boot in AGA we know a bit more.
If that doesnt work we can assume its something in pcigraphics. MAYBE