Alphanumeric devices

Hello everybody,
I am coming from a former “pure asterisk” installation (1.2, no FreePBX or whatever graphical GUI), and it has been working fine. Now I want to migrate to Asterisk 1.4 + FreePBX (up from a “PBX in a Flash” distro, you’ll find versions below).
The issue is that FreePBX prevents me from assigning devices alpha-numerical names, such as the ones I had formely assigned to my devices. According to Asterisk doc, the devices and the extensions had to be kept well apart,and only the extensions have to be assigned numerical values, while devices (declared in the [] brackets sections in sip.conf) can be alpha-numeric.

But in FreePBX, if I assign an extension an alpha-numeric value, I get an error.
Well, there’s an option , controlled by file amportal.conf, under the key AMPEXTENSIONS, which allows me to switch to “deviceanduser” mode (“extensions” mode is the default) thus separating the devices from the users they are actually using. But in either mode, the devices have to be assigned numerical values only.
With such constraint, I’ll have to rename every device and their credentials, which is not easy to me since they’re scattered around…

Any idea?
I haven’t find answers on the forum, or online docs
Thank you!
Post Scriptum: FreePBX is great

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