The issue that arises when disabling NAT on a device is that the router would also disable the DHCP functionality on the router, meaning that the IP addresses and DHCP would have to be run on the next routing device on the network. This is what AP mode essentially does, as it passes all management functionality to the next routing device. Without being the router that is providing the addresses and tracking stats, the AP in router mode would not know how to connect to a device.

Are there any specific features that you are missing out on when using AP mode? I can pass this feedback to our team to see if there is a possibility of seeing/accessing the info from AP mode. Also, if you have multiple ISPs for the same purpose, you may want to look at routers or switches that have the link aggregation features.