Hmmm. As default functionality of our RUT devices you can set let say the signal value reaches this and there is no connectivity it will automatically switch sim cards. So the solution that could work in this scenario of yours is using two RUTX12 where both of the devices are on failover mode instead of load-balancing. I suggested RUTX12 because it has two LTE modules that could be active at the same time where the device could also check the network connectivity with the different operators.
So the set up would be:
RUTX12-A (Op1 and Op2) LAN <------> WAN RUTX12-B (Op3 and Op4)
In this connection, RUTX12-B main source of WAN is mobile sim cards Op3 and Op4 when this sim card is not having network connectivity within the area it will switch to WIRED wan where RUTX12-A is providing network from Op1 and Op2 and RUTX12-A will be the one to verify which Sim card is having good signal reception.
I know this one is not really the best suggestion but it may be improved with custom scripting maybe like switch to Wired connectivity when SIM 1 and SIM 2 is having this RSSI value or similar situations.
Regarding how to do it via custom scripting you need to do it by yourself. Or if you are not able to do it you can request your sales account manager to do research and development.
Thanks and have a nice day!