An answer from Relic (
https://www.facebook.com/companyofheroes) :
The modding community is very important to us. However our first priority is to secure the integrity of players' online experience. Unfortunately as you note some of the modding abilities have been closed, and that is because they allowed for security exploits that had the potential to ruin the game for online players.
While most of our modders would never create a hack to cheat in competitive multiplayer, there are people in the gaming community who seek to profit off cheating (for example removing fog of war).
Our priority is to keep the game fair, and without cheats that could affect automatch and competitive multiplayer, while exploring ways for us to allow the great mods that we saw with the original CoH.
It is a slow process at times, and that can be frustrating. However we do wish to allow for more complex modding in the future, and we have been having conversations with our mod community at the Relic News forums which is traditionally their hub:
http://forums.relicnews.comIdeally we will be able work with them to support modding going forward and the inclusion of Steam Workshop, though just for maps now, opens up a very exciting opportunity for a wide variety of players to enjoy their work, as opposed to the more limited population of the original CoH who enjoyed the great mods created for that.