You think you're going to "dead bug" a processor capable of spying on a 28 gigabaud (or faster) link, by definition at line rate, into a device the size of an SFP transceiver? Actually let's back up one. You think there's a processor inside an SFP transceiver that you can attach a spy to? The things have as much brains as a battery charge controller. Their job is to provide stable DC bias to the receiver PIN diodes and the laser emitters, and in present datacenter units to have either 28, 56 or 110GHz of analog mo/dem bandwidth. To that end, they have a micro-brain in their ASIC silicon that lets I2C find out what's going on and how hot the unit is, that's it.
Now let's just snap our fingers and imagine that's possible. Oh, and there's also an entire bank of nvme drives to allow this "dead bugged" spy processor to store more than a millisecond of captured data. This also definitely fits inside the SFP transceiver, and doesn't parasitize more than the 1-2W you'll have available. What, exactly, do you plan to do with it now? If you're the SFP (and not the QSFP or OSFP) you're plugged into the host, but you have no access to it (seriously - *SFP transceivers are dumb).
Are you going to tell me that this "deadbugged" spy processor is actually an interposer with its own entire network stack that can inject outbound data? Because you know, these sorts of networks, they come with guarantees on latency that are either sub microsecond (ethernet) or sub 100 nanoseconds (infiniband). Good luck not stepping on timing margins like -that-.
More like, "with an entire engineering team and being handed power and cooling for free, I could insert an interposer into the rack that could spy on whatever line I asked the DCOs to plug into it."
All of which is a very long way to say you have no idea what you're talking about.
There's places in hardware threat actors can attack you. Those places are the BIOSes of your servers. When was the last time you updated your laptop's bios? If it's more than a year I about guarantee you there's multiple CVEs out for it that Fancy Bear or Fancy Panda could utilize.