Perhaps instead shooting off individual keypresses with some random chaff packets, it would be wiser to have constant interval, constant low data rate, (say 8 KBps) data rate trickling packets through and let the other side throw away pick out the needles from the haystack of no ops. Good luck finding a side-channel in that.
Sounds good until (for example) you find out the SSH client library wasn't queueing up packets ahead of time, but instead building them at send time, and a chaff packet takes less time to build than a real packet... so many ways to get side-channeled.
Crypto requires a good source of random entropy. I suppose if you want more traffic for obscurity, you'll also have to find more random bits. Without enough entropy, you'd sacrifice security for obscurity. Just my ¢2, ymmv, etc
