Is it possible to customise the appearance of the Ambiance theme just for one user?

I have read about the possibility of doing this:

sudo vim /usr/share/themes/Ambiance/gtk-2.0/gtkrc

but could something be done to change:

• just one setting

for

• just one user?

Perhaps changing something in the user's .themes directory?

Notice: I would prefer not to copy the full theme to the user directory, just to provide an override mechanism after the "global" theme is applied, independently from the theme if possible, but anyway just specifying what needs to be different, not duplicating the whole theme definition.