This is awesome!

before this line I would add something like the following.
<pre>
if is_integer(sshd_config_serverkeybits) == false {
  fail("sshd_config_serverkeybits must be an integer")
}
</pre>

 Not sure if you can evaluate the output of the function like this or if you need to assign a variable like
<pre>
$is_int_sshd_config_serverkeybits = is_integer(sshd_config_serverkeybits)
if is_int_sshd_config_serverkeybits == false {
  fail("sshd_config_serverkeybits must be an integer")
}
</pre>