It's a thing I've worked on a bit in the past. I had some code that would dump a table of all (ish) the vanilla sprite configurations for a main character to a .png file, along with the palette. There are ways we could arrange this such that it could be edited and re-imported to form replacement sprites.
However, there are a LOT of sprites to replace. Making one of these sprite sheets for a custom character would be really time-consuming.
There'd probably be a separate tool to export/import these to test with.
It's a thing I've worked on a bit in the past. I had some code that would dump a table of all (ish) the vanilla sprite configurations for a main character to a .png file, along with the palette. There are ways we could arrange this such that it could be edited and re-imported to form replacement sprites.
However, there are a LOT of sprites to replace. Making one of these sprite sheets for a custom character would be really time-consuming.
There'd probably be a separate tool to export/import these to test with.