While my problem is Pokémon-centered, I put this in the Graphics editing section because it can still be useful for NSMB hackers.

I explain, for testing purposes I changed one image from 4bpp to 8bpp (in this case Jolteon mini-icon).
I also changed the .ncer so that Pokémon icons use the 8bpp format instead of their default 4bpp format.

In theory, if my idea worked, I would be able to use 1 palette of 48 (47) colors for Pokémon icons instead of 1 palette to choose out of 3 palettes of 16 (15) colors, which would be quite the improvement as I would get rid of one severe limitation.

In practice, the image definitely shows in-game, but its dedicated palette only begin at row 3 (or row 1 in the second case).
For easier understanding I will call the beginning row the Relative Row 0.

Thus when the image is in 4bpp mode, it's all good:
Relative Row 0 = Absolute Row 3


But in 8bpp mode, the colors are counted beginning from Absolute Row 0, no matter what.
Relative Row 0 = Absolute Row 0



The same image might fetch its Relative Row 0 at different Absolute Rows according to the screen where it is loaded.

So I ask the following:
Is there a way to make a 8bpp image begin to count colors relatively to the first Row of its native palette, very much like a 4bpp image would ?
Or will Relative Row 0 always equates Absolute Row 0 in a 8bpp image and I am pretty much forced to use 4bpp images ?

I already had the gut feeling it wouldn't be possible, but it's nice to have the confirmation.

On the plus side I won't have to change back the 120+ icons I already upgraded.

Thank you for the honest answer.