I love the roms... i use them for almost everything when i can. one issue though, is manually typing all the values for code or copy and pasting into each rom, which can take forever if you have hundreds of roms.... if i was able to somehow have a file that i can automatically import into the rom, that would save a ton of time  im not sure if its possible...

I use for ROM 2 tools GPT and Libre office calc
For example i try  made sound track of zelda ( Overworld 1986) , so GPT create me a list of hex  for note . I have midi and I was crate a data in libre and coppy and pasting for 3 ROMS(16 s per one ROM) this method is suffice me

I saw your last pixel art and You used decoder 8 to 255 and you used logic ,for this , why ? You can use rom first 00-FF make column second 00-FF row and one 3 state buffer per enable ^^

I hope that it was helpful