Here is how my emulation looks right now:
The first three look somewhat plausible, but the last one looks odd. Judging by similar multicarts, the background should be blue, not gray, and the lowest parts of "N" and "1" look incorrect as well.
I just noticed that the palette format that I am emulating for this cart resembles the VT168's... :unsure:
And the IRQs seem to be expected one scanline earlier, but 32 or so PPU clocks later, than a standard VT03 (or MMC3, for that matter).
All of these changes would of course break existing VT02/VT03/VT09 games, although I could implement both, and use the very first register write that the game makes ($01 to $4304) to tell them apart.
NES 2.0 headers are nice, but Nintendulator should load the .BIN file just fine. The NES 2.0 header would have to specify mapper 256, and 4 KiB of PRG-RAM (possibly just 2 KiB, but they would then have to start at $6400, which is implausible).