I hated the trade initially and talked myself into it. If it fell through I would be fine getting the Brooklyn pick back and Zizic. IT will get surgery and miss the season in preparation for free agency, and Jae can be moved to any team in the NBA if he has an issue coming back to Boston.
Remember, Danny has said repeatedly that some of the best trades are the ones you don't make...
In the scenario you describe our starting lineup is
Smart - Brown - Hayward - Morris - Horford
The Celts win 40-45 games and lose in the first round.
Also they probably have a bottom 10 offense.
Basically, a very different season than we thought we'd get to watch.
Additionally ... rather than having an elite scorer running our offense for the next 5 years, we have ZERO idea when or how we're going to have a legit lead scoring option and playmaker again.
There's no way to spin this as a positive scenario if the trade gets voided.