When altering unit data in the object editor, do it for each map, not using the campaign object editor. If you are using the same data for each map, you can export object data from one and import them into all the rest. Takes only a few minutes to do that.
The import archive, though, is a different story. With campaigns, all imported material has to go into the campaigns import archive, not for each map. Once all your maps are loaded into your campaign, you can then assign new model files to units ans such. They will show up then.
Good luck.
-VGsatomi