The APS-C sensor size along with the associated camera size.what do you expect to gain going aps-c?
If you already have an a7rII and lenses ... I would just go with A7II or A7SII
I had an A7II and sold it. Since I started doing commercial photography my practice has been to have two bodies that are the same on a job. Back in film days it also meant two lens options. Now, with quality zooms I'm inclined to keep the second one handy as backup.
The A7RII and A7II were just enough different to be mildly frustrating on the job if I swapped back and forth. Or even as a backup. So I sold the A7II with the intent of buying another A7RII.
Then Sony threw a wrench in the works by announcing the A6300. It has some appealing capabilities, offers the smaller sensor/file size and works interchangeably with the lenses for the A7RII, including via the adapters I have.
The only additional lens will be one ASP-C zoom, for a compact base setup.
And as Vivek mentioned I'll be able to use the Nissin Di700a system interchangeably as well.
It really just boils down to should I buy one more A7RII or two A6300s to complete my kit for events. I'll always want the A7RII for architecture, art documentation and personal work. Which also suggests, that unless the A6300 has something that really stands out, I'd be happier with a second A7RII.