I was privileged to have my project approved. Whoohoo

So, my outline of a plan once I have the hardware is as follows.

1. Bring up a basic linux system -- Gentoo?
2. Bring up the networking system.
3. Get simple ssh access across ethernet working.
4. Configure my voice modem.
5. Trial a simple voice mail system to prove all of the voice modem subsystems. This will be based initially on the vgetty and mgetty software.
6. Setup caller side menu interaction.
7. Once functional, explore options in redirecting voice to headsets. Initially just a headset pluged into audio ports (headphone / microphone).
8. Setup bluetooth dongle with 2 bluetooth headsets and determine how to dynamically redirect an incoming call to either headset.
9. Optimisiation
-- Attempt rebuild of functional system with uClibc. -- Attempt to reduce footprint of entire system to a very small compact flash card size.
-- Explore compact enclosure and compact power supply options.

Comments.
This all essentially follows my initial presentation, however I have some concerns with Asterisk. Many linux user groups have comments that Asterisk requires much setting up.
This may mean that Asterisk my be difficult to port / bring up on new hardware.
I will pursue the Asterisk port if other options become restrictive or overtly complex.

D.