Thanks a lot!
And guess what - it works! (G500 with 3110m, OS X Mavericks 10.9.2 Clover, ig-platform-id 0x01660004)
Just a clarification: This file (the AppleIntelFramebufferCapri.kext) obviously is a patched driver that enables the Laptop display port on 0x05 for that platform-id. (there's some guides out there how to manipulate port settings per platform in the FramebufferCapri)
Said ig-platform-id (or IntelFBCapri as it's called in Chameleon) only expects 32MB initial Video RAM as opposed to 64MB with the other working (but flickering) ig-platform-id 0x01660003.
The caveat with this patched Capri and the platform-id used now is that it only supports one display, i.e. the built-in HDMI-Port of the notebook is unusable - as opposed to ig-platform-id 0x01660003 where it is usable but as mentioned by David John the internal display is constantly scrambled/flickering (because parts of the Video RAM are used by the OS as conventional RAM).
I'm looking into getting my BIOS patched to be able to set the Video RAM to 64 MB and use ig-platform-id 0x01660003. Will report back.
But thanks so very much - took me three days to get that darn thing working. HDMI-Out is nice to have, but to me right now not a must - so I'm happy :-)