We are only interested in doing FACS, no Proteomics analyses. Would the Stable Lyse V2 and Stable Store V2 System suffice for FACS? Or Do we need the Proteomics buffer as well for doing FACS?

To use the Stable-Lyse Stable-Store reagent system to bank samples (whole blood etc) you only need the Stable-Lyse buffer and the Stable-Store buffer.  You do not need the Proteomic Stabilizer PROT1 (that is a separate reagent system for banking samples).  Here is a link to download the standard Stable-Lyse Stable-Store protocols: 

 https://www.smarttubeinc.com/protocols/stbl/ST_SLSSP1TF-150203.pdf