Configuring to use as legacy answering machine

Just wondering if anybody can help:
I would like configure the system ( TrixBox or Emastix) to support legacy answering machine mode - when call comes in and sent to the voice mail user can hear the voice mail that has been recorded on one of the predefined IP phone ( extension - on the speaker phone) and if he picked it up then conversation is continue with the caller and message got deleted.
So basically hear recorded voice mail on the IP phone speaker phone and then interrupt recording if picked up.
Appreciate any help with it,

I am thinking that calls would go to a recorded conference with a script to cancel the recording if the number of connections is two.

Sure seems doable for a Guru.