> If you don't know how to harden SSH

then you do not open it to Internet. Otherwise you patch aggressively, you use ssh keys and not passwords and you move it to some random port to hide it a bit (it actually helps)

> logspam

you can filter this out in your log management tool

> CPU burn

if this is your concern, then you have a hep of issues you need to address. I have never seen a CPU perf hit because of such behaviour (there are cases where it happens, butthis is due to a vulnerability of the service)

> network traffic

the packet is here already, there is nothing to reduce