BOS: Tyler Zeller, James Young, 2016 Boston 1st (or DAL 1st if necessary)
DEN: Danilo Gallinari
That's how we add an impact guy who fits what we need and we lose almost none of our current roster. Zeller is still a pretty good player, and I bet they'd love anyone not named JJ Hickson to be there back-up C going forward. He would fit really well here, he'd give us another go-to scoring presence and he's locked up on a reasonable deal. I think that's the kinda thing Lowe is talking about. Impact players aren't necessarily stars.
This is a realistic and solid idea.
The thing is, this team is predicated around it's defensive toughness.
If Gallinari comes in, he replaces Crowder as our starting SF and we immediately lose our defensive identity.
If Gallo comes to the C's, then IT needs to go to the bench, or Crowder goes to the bench.
You can't have IT and Gallo with just Smart and and Amir out there as the two defensive beasts.
The guy that comes in is going to fit our scheme of defense, loads of three point shots and heavy ball movement.
Gallinari, although a great player who we could- as you highlight- get for basically nothing, doesn't fit that defensive identity. He's also paid 17 million a year and I can't see Danny giving up that cap room because Gallo would be signed until 2018 (this year, next season and the season after).