Look at the debacles of veao and avio. Those two third parties have struggled to keep up with the development of DCS and have continually failed to update their products citing ED as the problem. These two developers should be privy to the development of the core sim yet fail. Now we are to have community modders charging for DLC! With no knowledge of what changes are in the pipeline? Imagine a community modder like Tom whose has produced a lot for the community. 1 change in the core sim could mean he has to change everything he has produced. That is a lot of work to do for an unforgiving community.
Citing FSX and P3D as an example, FSX has a finished core, P3D has not. A lot of FSX developers do not produce as much for P3D or update their core as a priority purely because P3D is still a work in progress. The core is updating frequently and third parties simply do not prioritize P3D updates.
The problem with DCS is that it is a work in progress with a tagline "everything is subject to change". Who in their right mind is going to pay for community modded content when that content may very well be unusable after the next patch/update.