I am building my personal private cloud. I am considering using second hand dell optiplexes as worker nodes, but they only have 1 NIC and I'd need a contraption like this for my redundant network.
Then this wish came to my mind. Theoretically, such a one box solution could be faster than gigabit too.
Absolutely this. I learned so much on my homelab that at this point has more resiliency than some medium businesses (n+1 switching, vSAN for critical VMs, n+0.5 UPS for 15 minutes)