I don't understand the point of "not specifying output files". First: I just used your client and it worked, it is great work, thanks for that! But the one thing I did not understand was the -f options. Why don't you implement an (in my eyes much easier and common) interface of --output-key path and --output-cert path?

Having to script that with symlinks is nothing I can't do, but something that sucks a bit. Otherwise the crontab would not even need to call a bash-skript wrapping that stuff, it would be just your client with proper parameters. I'd much prefer that.