It has been requested before to allow extensions to define their own keymaps:
This was rejected because of concerns for conflicts: what if Nautilus later wants to use the same keymap? What if multiple extensions try to register the same keymap?
I think an easy solution would be to use ~/.config/nautilus/scripts-accels. This file already allows to define keymaps that trigger scripts - which means it already overcame these concerns. I assume that this is because the end user is the one setting the keymaps, not a plugin author, so there won’t be any conflicts with “other” extensions and if Nautilus itself adds a conflicting keymap the end user can just replace their own keymap themselves without having to wait for the extension author to do so.
So what if instead of letting extensions define keymaps directly, they could define commands that can be triggered from scripts-accels? That way the users will be in charge of setting these keymaps, which should address all the concerns about keymap conflicts.