Has anyone done this and then gone back and added MoCa bonded adapters to create a LAN? Would ther be any issues with the WAN operating at 1000 MHz and then adding another adapter to create a LAN at 1150 MHz?
I have not actually done it, but it should be doable. What the original poster did was reconfigure the frequency used by MoCA adapters to the D High Band to get them away from using the MoCA LAN frequencies they are set to by default. This was necessary in his case because he was also getting Verizon FiOS TV service and that gets the video on demand and guide info to the Verizon set-top box(es) from the coax from the router on the MoCA LAN frequencies. The theory is you should be able to have up to 16 MoCA devices on the coax (where the router is one device and each STB is another).
If you have the G1100 router, FiOS TV service, and added another MoCA adapter (I assume we are still talking about the ECB6200) without reconfiguring it, it should join in with the router and STBs on the LAN. You should be able to connect a device or switch to the Ethernet side of the adapter and have Internet service. That would not pass Gigabit ethernet (if I recall correctly) because it is unbonded MoCA 2.0, which I think tops out around 400 Mbps. (Older equipment like the MI424WR router and older STBs were MoCA 1.1, which was even slower.)
If your goal was to set up a Gbps LAN with MoCA adapters, you would probably have to reprogram a pair (or more) of the ECB6200s to the D High Band just so the frequencies they are using are away from the MoCA LAN the routers and STBs are using (at a slower rate) and the MoCA WAN (if you have coax service rather than Ethernet from the ONT). I don't have FiOS TV service, so I use a pair of these without any reprogramming necessary since there is no contention.