The Leafs are committed to Marner, whether they like it or not. His NMC gets exercised immediately, not because of destination but purely because he's exactly where he wants to be, making the most amount of money he'd make on a contending team in his hometown.
Honestly the only options Toronto has are 1) sign him to an 8x$12.5 or more, or 2) watch him walk after next year. If they wanted to shake things up, they had to trade Marner, location-independent, before the NMC kicked in. If they wanted to shake up the core, they had to do it before Nylander signed the extension. Toronto is stuck, they'd better hope it works.
For Columbus: I don't think this is the year to go get a big name. The idea is right, but I
explored the idea earlier. There's not really any good options right now that fit the timeline, either because they're not impact enough or frankly not available.
The rest is fine, the ideas are good, and the values look okay. I just think the team, given the market, is better served just making the picks, waiting, and letting the kids develop.