I think that my idea of it destroying Gollum immediately is possible but a bit far fetched. However something that I'm more certain of is that the destruction of the ring would have overthrown Gollum mind entirely. I'm not sure how his greater insanity would have changed him but the ring had such a hold on him that I don't see how it would be possible for him to stay sane (I realize that Gollum had little if any sanity anyway). So without the ring there is little if any hope for him.
The ring was Gollum's only point in living (except perhaps the occasional fish
). The ring had only a stronger hold on one person and that was Sauron, and we know that it destroyed him. Gollum would have nothing left to live for, if his existence can be called life.
I think that there was some good in him left, and Gollum came close to embracing that part of him but he couldn't Similarly Sauron came close to repenting of his evil but didn't and resigned himself wholly to evil. If Gollum had found some redemption than I think that the destruction of the ring could have possibly given some curative effect on him. However, it is my opinion that Gollum, like Sauron, gave in and wholly resigned himself to evil. Gollum killed the remaining shred of Smeagol when he went back on his promise and attempted to kill Frodo. So instead of helping him it would have completely overthrown him due to the actions he took.