No, a g729 module would not need to be installed if everything remains g729 and no translation from another codec is required.
Wonât the OP need a codec to convert the files to g729?
If at any point Asterisk needs to transcode (like to slin for a conference) wonât that necessitate a codec?
He can record them from scratch, using his G.729 capable phone to provide the microphone.
Yes there are lots of things that will breach the given assumptions. It is possible to design for pass through, but that does mean you have to understand how Asterisk works with respect to transcoding.