M3 Control Panel is our CP we have designed in house. We take feedback from our clients as to what they would like to see added and we spend the time coding it into the next CP version. It currently allows you to add/remove websites, one click wordpress installs, add/remove emails/aliases, change passwords, add a DB, backup a DB, etc.
Here is a walk through from a couple versions ago:
http://www.m3server.com/m3-control-panel
Currently we do not have a direct html coding included in it, but I wil let you know that it has been requested and is being worked on adding very soon.
By using our control panel we are able to keep costs down on our packages as we don't need to pay a third party license fee.
Any other questions, please let me know or contact me directly.
Thanks
Chris