I don't think it's wise to move a defenseman like Parayko for a winger, unless we're talking about one of a handful of wingers. If Armstrong was looking for a one-for-one trade then I'd hope it was targeting a centre.
If we had decided to extend Pietrangelo and move Parayko, then I'd prefer to target younger assets. As
@Blueston said, something like Broberg, Puljujärvi & the 14th could be the basis for a deal, assuming that our scouts really liked Broberg.
With the talk that the Oilers are shopping Larsson? Larsson, Broberg, Puljujärvi & the 14th for Parayko & Kostin wouldn't be terrible. We significantly downgrade Parayko, but get a replacement is capable of 20 minutes a night (when healthy) and should be a good partner for Dunn/Perunovich. We swap Kostin for a winger with a higher ceiling. Then we have a couple of prospects with high ceilings that hopefully help us get younger, or we can flip for something that helps us in the short term.
Again though, preference would be to keep Parayko long term... but, if we're only going forward with one of Pietrangelo or Parayko, these options are far preferable to losing Pietragenlo for nothing.