Hi, Tony,
I have played with CS Proxy about half a year ago, and it was a really excellent product. To those of you who are not very familiar with it, CS Proxy acts a mirror for config server, so that a multisite user could access CME without going all the way to the main site. On top of that, you could really do cool things with security without adding three billion security definitions to every level.
First of all, when Config Server goes down, config proxy switches to readonly mode. Since config server DOES support a warmstandby, what you can do is create a confserv_backup and make it run in a warmstandby mode. (Make sure you add [lca] section to the confserv.conf ) . Then, your config proxy will switch over to the backup config server and will be just fine.
Why would you want to run more than one config proxy on the same machine? I don't recall reading anything about config proxies being able to operate in a standby mode, but in the worst case scenario, just have more than one config proxy, preferably one per machine.
Here is a good question why would you want to have a backup for a config proxy? In the worst case scenario, you could always use the main confserv, can't you?
As for the load, it is really hard to tell, because it all depends on how active your CME is. In most cases that I know about, it is not that bad at all.
Anyway: can cs proxy be running in a warmstandby?