You could probably do the encryption very cheaply from a latency perspective (use AES to generate a key stream that you XOR with the output data, which could ea

You could probably do the encryption very cheaply from a latency perspective (use AES to generate a key stream that you XOR with the output data, which could easily fit on a sending/receiving FGPA without introducing any significant delay), but in general I would think that it is far more trouble than it is worth. All these features would require testing, and availability is pretty important for this kind of stuff.