As of 2.36c (extASM500236c on the dev site), Service_ModeExtension now calls translate_VIDC1_to_VIDC20 instead writing to VIDC1 and relying on the abort to handle it. I've not tested yet though.
As a consequence, I've also split the code so the Pi version doesn't process the extra commands in a type 1 list specifying the pixel rate etc. and removed all the VMOD/RMOD/FIFO/HVsync code from compiling into ADFFS500.