It will really depend on how Bethesda implements it. To me, it seems they are just trying to get employees for creating content without actually calling them employees (and giving them the legal benefits they would have as employees), not to monetize mods. If the submissions are really going to be QA/reviewed and supported, it's unlikely that they would be worth for every $2 texture or shader tweak, this seems to be more aimed at bigger stuff, "DLC" size, like Endereal or Nehrim (which are free, but you get the idea). The additional benefit for Bethesda is that they get a chance to enforce their micro-payment currency onto any buyers, opening a world of other purchases for the same buyers (removing initial barrier).
If they implement it badly and make it essentially Steam Greenlight, then it's going to be a shitstorm alright. If they take this as an opportunity to make its kinda-employees sign NDAs and prevents mod creation outside the program, it's going to be an ultra-shitshorm.
Either way, I don't think paid mods are necessarily a bad thing - developers were screaming the same about Steam "refund" system and how people would just refund short games, but statistics prove otherwise and sales have actually increased (allegedly), so the obvious outcome is not always the real one.