BRIA CLOUD extension is missing some important use cases

I have a FreePBX 12 system with BRIA CLOUD mobile user accounts and plan to use BRIA PC clients as well. The current implementation of the BRIA module allows BRIA softclients to be used only as "backup" devices for an IPphone as main device, but not to replace IPhones.

As long as a "main" device (IP phone) is configured and has been registered once (using the main extension number e.g. 45) then they can both be reached (forked call between both extensions 45 and 9945).

However when there is a "main" extension configured, but never registered, then the BRIA user can't be called (status : unavailable), neither on 45 or on 9945, while on the other hand this moble user can make outgoing calls (as it is registered with a 99945 extension).

Strange remark: for extensions with both devices 45 and 99945 configured, and when the main device is deregistered or unplugged, the mobile device remains reachable..???.

I have 3 use cases of which only 1 is working as wanted:

1) user with IPphone and BRIA mobile device : no problem as explained above

2) user with BRIA PC client and BRIA mobile device : not possible as they both would need the same 999XX extension. See PJSIP remark below.

3) user who only has a mobile device : he can make calls, but is not reachable

I tried using PJSIP in stead, which in theory should offer a solution for all above use cases because multiple devices can register with the same SIP account, but due to the fact that BULK extension input (CSV) does not work (ref my other reported issue 8518), and the fact that BRIA module is based on SIP_CHAN + AGI script for forking (using the 999 prefix method), this is not a valid way either.

Personally I see two ways to resolve this:

1) with SIP-CHAN and AGI script : allow BRIA users to be programmed with and without the 999 prefix - while 999 is for the "backup" user. It is probably possible to leave the prefix empty to get all BRIA as "main" extensions, but this should be done per extension, allowing some BRIA clients to become "main" extensions and other "backup" extensions.

2) with PJSIP : no need for AGI with 999 prefix, because multiple devices can register under the same SIP account, so the "main" / "backup" issue doesn't exist here. Each extension just needs a BRIA flag to allow provisioning via BRIA CLOUD. This solution also needs the fix for issue 8581 for the mass provisioning (Bulk extension via CSV).