This configuration, as described in the prior 10 parts, has been serving me well for at least the last two years, so it is a proven design. There are, however, some things to keep in mind.
This is not supported by Verizon. Or me, for that matter. If you ever have an issue that requires you to call Verizon for support, you may have to revert to a configuration that they support for them to assist you. (Basically, this means plugging your Ethernet drop directly into the WAN port on the back of the VZ router.)
Be cognizant of changes to your WAN IP address. If the WAN IP address changes for any reason, you will need to go into your secondary router and reconfigure the various items that refer to this IP directly to use the newly assigned IP. Even in such a situation, the primary router should pick up a new DHCP lease and your home network clients, at least, should work fine.[footnote]
Eventually, the DHCP lease for the WAN address will expire and the primary router will try to get a new one. When that happens, if the DHCP server issues a new address then the router will start using it and network access will resume.
I have had Verizon change my DHCP assignment once (due to a change in the IP address block assigned to my area) and I had to manually reacquire a DHCP lease at the primary router because the old lease hadn’t expired, but the address space had changed nonetheless. I speculate that Verizon probably has a way to force their own hardware routers to release/renew leases on demand, which they would naturally do right before making a network change like that.[/footnote]
As a practical matter, WAN IP changes are unlikely to happen very often unless you routinely have protracted periods of time when your network gear is powered off and/or not connected to the FiOS ISP network. It should be possible to configure some kind of automated process that will fix all these bits for you across the network when a WAN IP change is detected, but I haven’t managed to put that part together yet.
I sincerely hope this is helpful to someone!