Per my recent comp.sys.apple2 postings, I will be attempting to use the Wei-Ya ACV-011 "Cherry Master" JAMMA-to-SVGA converter board to get output from the IIGS. It accepts RGB+composite sync, as well as 12VDC, both of which are available from the IIGS, allowing the board to be mounted inside the case. For now, the plan is to cut up a 15-pin Mac monitor cable and run the proper lines into the converter board, and see how the SVGA output looks. More on this when it arrives.
The CV Technologies GS Memory card (halfway populated, I'll do the rest with chips from GSE-Reactive) arrived today, with a fully-populated Apple Memory Expansion card piggybacking on it. Neat.
-Chris