Here is the long answer: An editor is out of the FirstStrike teams hands. DICE has never released an editor for BF2142. If an editor is not released with the final BF2142 1.4 patch, there most likely will not be one.
The team's mappers uses the BF2 Editor with some complicated work arounds.
Here is the 'Leviathon' workaround for setting up BF2142 as a mod to work with the editor (Be warned, its complicated): http://bfeditor.org/forums/index.php?ac … entry55806
But, the editor will create a map with BF2 settings and you will still need to make code changes to set it up as a BF2142\FirstStrike map. The preview and load screen settings are different between BF2 and BF2142 games, for instance.
Then there is the issue of creating shadows (lightmapping). Since FirstStrike lightmap samples have not been setup yet for use with the editor, one of the team members has to use a modeling program like 3dsmax or maya to lightmap.
Perhaps one of the team's mappers can post instructions on how they have the BF2 editor set up to create maps for FirstStrike?