At this point, I think FC2 has the best game editor around. Even with African pieces, gamers have designed out-of-this-world maps. If more games offered an editor, I'm sure they would have a longer shelf-life as well. If FC3 is still in post production, then these are some improvements that come to mind...
Option to play against bots.
Move the info box from the center of screen to the top or bottom margin.
Enable friend invite during game.
Ability to shoot while reviving teammate.
While hosting, show if map is being downloaded from server or host.
Smarter map search when hosting, alphabetic by author or title.
Editor Settings preset.
Set which weapons are available for a given map.
Access to ALL pieces, villagers, animals and textures from single player.
Comprehensive inventory grouping of objects.
Waterfall, steam and fire emitters.
More interactive objects which players can move around.
A set of building facades, to help save processor speed.
Re-sizable blocks that accept textures and/or color choice.
Re-sizable occlusion blocks, or smaller occlusion pieces.
All physics pieces activated by any player, not just the host.
Control the water height by grid, rather than by the whole map.
Choose water behavior, color and murkiness.
Adjustable lamps and light fixtures.
Will not validate if the performance meter is in the red.
Lower the strobe intensity of selected object.
Author's description of map added to thumbnail and stats.
Overhead map display in lobby.
Allow 2 editors at once, or allow 2nd editor as observer.
Comprehensive editor guide.