After a weekend's study, some progress of netmerc was made:
The model-1's geo processors are also capable of triangles, in addition to quads.
The flickering background is still a headache. It seems related to v60 cpu emulation -- from disassembling, a mov instruction seems to copy the lower-word value of memory addressed by SP to palette no. 0
I'm not familiar with v60 cpu. Any friend would like to take a loot at it?