Well since i have already two managed switches for my vlan configuration, and the poe cams should all be on the same vlan, i use a normal unmanaged poe switch for ~ 35 €. I looked into the Surveilance Station shortly, could not find out if you need to pay for that (as far as i understand you, you need to pay / get licenses for every camera?). Also i don't own any synology NAS, so that would mean additional costs. The NVR from reolink with 2 TB was (in the bundle) only around 175€ (or 175$ including tax, over the thumb), so adding 35€ for a poe is no big deal and should be cheaper then a new synology nas plus disk, or an older used one.

I still don't know completely if this will work, but i'm confident at least :)