It might be a little early for this idea.  When creating new units I can see that there are going to be some favorites that I'd just be creating over and over again each campaign.  Is there a quick way to implement packs of player pre-designed units.  

Maybe a check box on the design screen that will make it available to every world.  This way you wont have to rebuild the same sets over and over.  But it will limit the odd-ball and just messing around units to the world they were created for.

Also the ability to edit the list of what can be exported to a new campaign.  I can see the fun in creating new and odd-ball units as experiments.  I can also see the frustration of having those units stick around crowding up the interface.