There are two types of Nelson to Colorado deals I can imagine: the simple Nelson for futures, or a blockbuster (not involving star players, but a lot of pieces). The latter seems incredibly unlikely.
What I don't see is NYI taking Johansen back. If that's what COL needs, NYI should deal Nelson elsewhere, or keep him. They can always deal him next year. They wouldn't be able to deal Johansen's contract. It's a non-starter.
I don't see Byram being a good bet for NYI. If he stays healthy & breaks out, NYI will be in a tough spot with Dobson + Byram contract negotiations happening at the same time.
Last, I think Johansen and Nelson would work really well as linemates.