R7000 as router, with Internet from 4G mobile phone hotspot

I have a R7000 router connected to a separate simple ADSL modem.

The problem is that every now and then the landline internet goes down, and I have a complex port forwarding / VPN security set up which takes a while to recreate when I reach for my DC112 ( smart cradle )

I want to keep the  R7000 as the central router because it  has a strong network signal and powerful processor for internal lan, and I dont want to waste time  setting up another router with usb 4G modem/sim chip slot when this happens. ( The Netgear DC112 Smart Cradle is not as powerful as the R7000, even though it does have 4G failover, otherwise I would just use that all the time)

Is there a way to quickly use a 4G mobile phone internet access? I saw a youtube video that did this with a different brand router using WDS bridging and mobile phone hotspot.

Or is there a new router that is more powerful than the R7000 with 4G sim chip failover?

Thanks.