Feature request: Large modal dialog inside a small modal dialog

Feature request: Large modal dialog inside a small modal dialog

If I open a small modal dialog and in this dialog I open another large modal dialog, then this second large modal dialog is displayed inside the first small dialog. It doesn't look very nice, as scroll bars appear.
How to make second modal dialog to look "detached" from the first dialog? So that if it is higher or wider than a parent dialog, it still would be displayed full size, not inside parent dialog.
Dialog has option appendTo, but if I attach second dialog to top.document, then it doesn't work correctly (incorrect position, moving, close method doesn't work)
Thanks!