For me a minimum (already useful) addition would be to have "inside" and "outside" margins.
Inside margins would be added to the right margin on even pages and to the left margin of odd pages (and vice versa for outside margins). That already would allow for some neat tricks. But having a full range naturally would be much cooler. I just imagine that the UI is non-trivial for switching between definitions for one style depending on whether you are on an odd or even page (because you basically need to be able to switch within the context of a single definition).
For me a minimum (already useful) addition would be to have "inside" and "outside" margins.
Inside margins would be added to the right margin on even pages and to the left margin of odd pages (and vice versa for outside margins). That already would allow for some neat tricks. But having a full range naturally would be much cooler. I just imagine that the UI is non-trivial for switching between definitions for one style depending on whether you are on an odd or even page (because you basically need to be able to switch within the context of a single definition).