I've been messing around with the ISPConfig. I at least know how to mirror it.
On your second server, if you have ispconfig installed, uninstall it. Run the installer again in expert mode.
Use your database settings and such and you will be prompted to join the server with your first one.
Note: You need to make a mysql user with privileges to the ispconfig database on server 1 that server 2 can connect with.
It should work okay.
You don't need to install the web interface or any option you do not want to replicate.
You can now go into your ispconfig on server 1 and select server 2 from the System -> Server Services. Check all that applies and use the dropdown box to mirror it.
As for replication.
I did a bit a digging and falko posted about mysql replication that would achieve the replication aspect.
I'm sure we can get it to work properly.
Hope this helps.