Leandro and KitsuneKnight are each working on offline Mission Architect Editors. Leandro’s is going to be small and self-contained, so that it can be easily used at work (no trace in the registry, etc.). KitsuneKnight’s is going to have a lot of bells and whistles and the kitchen sink.
A preview version of Leandro’s Editor can be found here:
http://www.futurama-madhouse.com.ar/cohoma.exe
This thread, on the official forums, has some discussion and screenshots of his early editor:
http://boards.cityofheroes.com/showflat.php?Cat=0&Number=13243811&page=0&fpart=all&vc=1