There's some (to me) interesting work in this area. See for example this talk[1], where they show how a RISC-V CPU with a narrow and slow PCIe link can orchestrate the direct transfer of data between two PCIe devices (say NVME and Ethernet card), saturating the x16 link between them.

[1]: https://www.youtube.com/watch?v=LDOlqgUZtHE (Accelerating Computational Storage Over NVMe with RISC V)