Modem/Router for booting from USB or PXE

Anyone knows an openwrt supported modem which can be booted from USB or PXE or other kinds of external media instead of the onboard NAND? Modem needs to support VDSL2.
Maybe changing the uboot config is already enough. But maybe you still need drivers.

The only supported VDSL2 modems are using the lantiq vr9 SOC, which doesn't boot from USB - basically no classic router SOC does. Yes, it might be possible to use a modified u-boot with USB support, but there you'd be on your own (at least the lantiq SOC is unbrickable).