I wouldn't say a professional team is needed by any means but a group is probably the best way to go. A real jack of all trades type of person could do one on their own. Conversations and scripting seem to be on about par with the other games.
Area creation is along the lines of NWN2 perhaps even more difficult from what I've heard (also an on going problem with lightmapping.)
Things like the Morph editor area easily mastered and really can add a nice level of change to a module.
The cutscene editor is just tremendous and not terribly tough to use (though tougher to master).
The actual system of making modules (database vs file system) take a lot of getting used to and has some advantages but some disadvantages as well.
One plus is that it has been out long enough so that there is some level of expertise on the toolset forums so road blocks are much more easily circumvented.
As for the 'market' for modules. From a module maker point of view Dragon Age is a HUGE untapped source for players.
I think a small team could put out some really good stuff. It's just a matter of finding the people that like to do each of the tasks.
I'm working on cutscenes for a couple of modules in progress but I still have an idea and a general design of a module I'd like to make. One of these days I'll have to put out the recruiting call.
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