My problem with moving Methot, regardless of his injury history, is you've created a hole to fill one. Your D already includes (2) 26 year olds, 24 year old, 23 year old, and a 19 year old. The answer for me is to not slide Heatherington in as the #6. I really like the guy, but that's too young of a group. I'm fine with him sliding in for injuries. Maybe he's a full time guy the following year, but I think a veteran with this group makes a ton of sense if they are trying to be a top team next year.
There are obviously some UFA options. I've always really like de Haan. He's still young, but he has 5 year of experience. The fact that his season was cut short by injury ... IDK .... might make him willing to do a shorter deal. I doubt it. Hamhuis I guess could be a short option.
Last thing though, I have a hard time seeing Methot bringing back the type of impact forward Dallas needs. Dallas got him for a 2nd round pick 3 years in the future, and that was before he had another injury riddled season. You, might be able to recover a 2nd round pick, but I don't think you'd get a scoring winner.