I won't say that turning a TDA into a de-cock only is impossible, but it's not something I would try. Particularly since the parts for both types of actions are getting harder to find. The spring on the safety in the link requires a corresponding hole to be drilled into the slide. Again, I wouldn't try it.
Howard
P.S. We were shown that style of de-cocker in one of the armorer schools I attended, but I don't believe S&W ever actually manufactured pistols with it. If they did, I never heard of/saw one. There might be a reason for that.