@ffmancera have you checked with the #OpenWrt people? One thing that would come to my mind: We used to have embedded devices with separate kernel and rootfs partitions, where the kernel partition would have a fixed, limited size. There it would seem useful to be able to build as much as kernel modules as possible. We've had that issue before, not being able to update the kernel due to limited size.
But I'm not 100% sure if that is still the case or which (old?) devices that would affect exactly.