/etc/issue and /etc/motd files are in place, these messages display after the login. The ssh-banner messager suppose to come up before the login, before you type in the password. Does OnTap not support a "true" ssh-banner?
You're right this this isn't a Linux host, but there is a way to effectively restart services like "ssh" should you need to. I have used this on other services, don't think I've ever needed to do "ssh", but you'll get the idea. The command for ssh would be:
options ssh.enable off
options ssh.enable on
I've used this to flush and reload cached NIS information, as changed netgroups don't always "take" right away. Of course, change "ssh" to "nis" in the above, just to be clear.