I am also interested in this.
Except my list would look like this
Doesn't appear you can do this in the new Pages for Mac OSX or or iOS.
If not, a huge reason for me to stay with Pages 09. I initially tried the Mac version but removed it when it started reformatting my old docs. Now on my iPad I have been trying to re-learn Pages and Keynote and this is just one of the things I have found that I really need. Have found quite a few things that are nice but number lists seem pretty basic.