My suggestion, very simple: add a version of the <.phase toggle objects> command for a one-time deal.
For example: I want to copy current starting area to my own phase, however, I do not want future additions to be added as they come along (if any). I don't know what will be added; and if I build in the phase, I don't want it to overlap with anything I already built if future main phase builds come in.
Hope my suggestion made sense, please let me know if I need to clarify (: