I hope someone can help me with my setup. I have two WAN routers from different Internet Service Providers. I'll call these ISP_NAT and ISP_PS4 for the sake of this question. ISP_NAT uses NAT444 (CGN) which creates problems during matchmaking in online games, ISP_PS4 doesn't and is perfect for gaming but not as fast ISP_NAT which I use for every other thing.
ISP_NAT (Huawei B5141) is connected to a TP Link Archer C9 router which avails a WLAN network around the house, although the ISP_NAT itself is capable of broadcasting its own WLAN network. ISP_PS4 (Huawei LTE CPE E5172) is connected directly to my PS4 and is the only device using that connection.
The problem is, I have a Plex server hooked up to ISP_NAT which allows client devices on ISP_NAT/TP Link stream videos and whenever I need to connect the PS4's Plex client to the server, I have to switch its connection to ISP_NAT. Considering how often I switch between movies and online gaming, this is becoming a pain. And I'll rather not have the PS4 access the Plex server remotely as that will drive up my internet costs which is very expensive here in Nigeria.
I'm after a solution that will allow ISP_NAT and ISP_PS4 co-exist on the same local network allowing devices access each other regardless of which ISP_* they are connected to.
Is this possible? How can I achieve the desired setup?