I don't think GMs are dumb enough to take Kapanen or Johnsson as a centerpiece in return for a quality Dman. Would be a terrible idea in this NHL. Don't see that happening at all. Especially given that Toronto doesn't even have the picks available to bridge any gap in value..
Sounds more like Toronto is trying to get someone to bite on a stupid deal like that and is trying to draw some media attention to make it happen...
Objectively... if you're a rebuilding team with a defenceman that has a year or two left on his deal and can get Kapanen, Liljegren and Tornto's 1st next year, I think that opens a lot of doors in terms of quality defencemen.
You get a guy who's all but guaranteed to be a solid 2-way 2nd line winger who can drive the play if given the opportunity, making $3.2m for 2 years and still being an RFA afterwards. You get a right shot defenceman drafted 17th overall a couple of years ago, poised to step into the lineup immediately, with 2 years left on his ELC, and a 1st round pick.
Now, I'm not sure the Leafs are prepared to part with 3 assets of this calibre, and there is a further cap issue to resolve... but I see no reason why Kapanen or Johnsson cannot be the centrepiece for a high quality dman with some term.