I like the idea, but remember that the SLA with your fiber provider doesn't mean your fiber magically will come back within a few hours when someone in the street cuts through the cable by accident. Your clients will still experience downtime unless you have two fiber lines going in different directions - completely redundant. If you don't have that, I would recommend some kind of a licensed microwave link on your roof as a failover.
We have a fallback coax connection going another way, it's only 500Mb/100Mb/s but it does the job if the fiber is cut. We are also working on having a 5G fallback just in case, as 5G bandwidth can be quite high on short range.
Sounds like you have a pretty decent set up then. With all the redundancies in place (and hopefully power redundancy too, batteries, generator) you can run mission critical software from there.
