I like that we can now create our own list of custom page sizes, but how about a couple of simple enhancements:
I'd like to be able to reorder the list within the Custom Page Size dialog box; just a simple drag with the mouse, much as iOS allows you to rearrange lists by tapping and dragging to the new position. I like to keep my lists organized but I don't always create them in logical order; usually I do them on the fly, as needed, which means that related items are scattered all over the place, and the only way to put them in coherent order is to delete them all and re-enter everything after determining their proper sequence.
Allow renaming of an item within the dialog. You might even consider adding this to the "Edit" menu as an item that can be edited in the same manner that you can edit your output list, colors, etc.
It would also be nice to be able to set all the parameters of a new project as a new preset ( I am thinking particularly the margin guides, orientation, etc.) Heck, there are even types of projects that I know from the beginning that I will need a certain number and types of layouts, all of which could be saved as a document preset.