I don't think it will have the effect that you're looking for. Apparently what Valve learned from the whole thing was "We should have tried it with a new game, not one that's been out for years".
GOG would be a great competitor if they could get more of the major releases.
Valve can do whatever they want with their own games, I guess. Whatever they do, I don't think it will eliminate the free modding communities online unless they conspire with one of the devs (say Bethesda) to close the system and make modding only accessible via their own platform. Which would be an indication that they weren't too interested in ever selling for PC again anyway. In any case, if that were to happen, it would likely bring the full force of gamer fury down on them. I'd like to see them weather that storm (and it would be nice to see that sort of thing turned towards a noble cause for once).
At less than 40, my Steam library isn't even that out of control. Buying more of my games on GOG would be a dream, though.
It's not like people aren't trying. Might have to wait for Steam to expend more goodwill first, though. Every couple of weeks here we get a "Steam good, Origin bad" thread, which never seems to have any rational basis.
Steam's customer service has improved dramatically. Now when you request a refund, they spit on you before denying it.