failover script with dhcp-client-IF and one LTE-IF

hello there,

after searching a while:
i have seen a lot of scripts for failoverscenarios here. - most of them are based on ppp interfaces or static-configured next-hop ips.
in my setup i plan to do an bunch or routers with “one” preconfiguration, where i have around of 200 sites were are dedicated subnets for dhcp-clients configured.
means no static next-hop (for dhcp-clients) is known.

my question:
any experience or any scripts available from people who have may a similar requirement?

if primary fails (dhcp-client): check should be done by an specific remote host which should be available via this link. then increase distance.
if the primary is back, the distance should be decreased again.

thank you!

christian