This is indeed a good idea, but I have some technical concerns. As it stands now, your idea involves no port forwarding, and thus it is not hosted on the computer of the admin, but Mojang's server. Mojang's server hasn't exactly been renowned for their reliability, and further stress will just cause it to crash more often. You could have it so that the Minecraft client automatically port forwards, allowing the servers to be run on individual computers, but that opens up security concerns. As the situation currently stands, I think only the LAN servers could be implemented.
Your idea currently involves an extended 'setting panel' to change the numerous settings currently in the server.properties file, and it would be nice to see that added.