What would be the benefit of configuring SOFS with S2D on Server 2016?

S2D is uber-expensive for what it does in terms of storage-only deployment. It's Datacenter-only WS feature so while HCI scenario kind of makes sense - segregated / SOFS definitely doesn't. I'd leave things AS IS. If you absolutely want SOFS for whatever reason - look @ StarWind VSAN Free. It's much faster, more reliable within 2-Node deployment and... it's free :)