There is no need for a Plan B, our Plan A - which from my understanding was Horford - worked.
Horford has played his career as a Center, why would we look to acquire another Center immediately? There is no need to gut our team, when it is now clear that we have become a viable free agent destination, with 2017 Free Agent market looking great... which will also include KD again. Next year GS will have to find a way to max, KD, Steph and Iguodala... who I would argue is more important than Draymond.
The addition of Horford alone will drastically change how teams play us on offense and play against us on defense and is worth us being a 55+ win team.
There is no need for a plan B... we already got our fireworks!!!