Interesting - it makes me wonder what you actually intend to do with the UCx system.
If I remember correctly, phpMyAdmin is a tool that allows administrators to manage MySQL databases. But UCx is a telephone system, not a generic server that runs MySQL.
Webmin allows administrators to manage UNIX and UNIX like systems - UCx allows you to change system configuration data and perform system administration tasks that are needed for the operation of the telephone system via the management GUI.
If you want to add extra software packages that are telephony related to the UCx system, you should probably talk to E-MetroTel. They are responsible for the operation of the system and thus would need to ensure that the new package works properly with their software.
I am pretty sure that almost any user - and that includes the UCx admin account - can use the command /sbin/ifconfig.
The admin account has sudo access to /sbin/service, so you can restart the network from the command line if you really want. If you feel that a network restart is an operation that is needed frequently, you could suggest to E-MetroTel to add network to the Dashboard GUI applet that allows the administrator to start/stop/restart services.
The admin account has also access to the asterisk CLI (which is also available via the GUI - just look at PBX - Tools).
If you need a database server with MySQL, get a dedicated server. If you want the ability to manage each and every aspect of the OS used by your telephone switch, have the time to ensure that everything that is on the system is compatible, are willing to do all the necessary testing and have the time to support the system, just get a server and install something like the FreePBX Distro.
If you feel that UCx does not allow you to use some system commands that you absolutely need, you can always contact E-MetroTel and suggest to them that they should allow the use of the command(s) or to provide the functionality via their management GUI.
Let's look at something like Nortel/Avaya BCM or IP Office. Do you expect/need to have root access? Does Avaya allow customers to install untested software on these systems? Does Avaya allow customers to use these systems as database servers? I believe the answer is no. So, the question is - why do you expect something like that from UCx?
Hmm - if you can convince Avaya to provide root access to all their systems, I am pretty sure that many people would interested.
Happy 4th of July to everybody.