Divided chest GUI

This idea started from the fact that I wanted to make a resource pack where GUIs didn't had slot borders, and the only border would be where the slot ends. So the inventory instead of being a 27 cells thing would be a single big box with borders only around. I did this for most of the things but it bugs with chests. Chests use generic_54.png for their texture. Double chest use the entire texture, [single/normal] chests cut the first 27 slots of the file. If I make borderless slots large chest GUI, with a normal chest the bottom border disappear. To fix this, I have to add borders between the first and the last 27 slots. But this isn't all. In servers with custom GUIs plugins this problem reappears with 9 slot GUIs. It would be good if instead of one generic_54 we had six files: generic_9, generic_18, generic_27, generic_36, generic_45, generic_54. In 1.15 you made divided chests (chest_left and chest_right) instead of one single texture, so why you shouldn't make this?