[ohazi]

Exactly, use the right tool for the job.

FPGAs and microcontrollers are really good for meeting (and verifying that you're meeting) hard real-time constraints.

Network connectivity (by definition) can't be real-time, so you wouldn't want to run a network stack on the real-time core anyway, even if you could.

Instead of adding another non-real-time microcontroller for networking and making it sweat, go with an application processor and just treat it like a dumb modem that happens to know how to handle VPN traffic without exploding.

There are application processors like the i.MX7 and the STM32MP1 that combine a Cortex-M4 and a Cortex-A7 on the same die for precisely this reason (and similar FPGA fabric + PowerPC / ARM Cortex-A? products from Xilinx and Altera for even longer).