Padraic: <<Question: are all 1000 people in on the project, or is there just
a small cadre of conlangers in on it?>> 
I don't know. What do you think most humans would prefer? What do you think
would work best?

Padraic: <<I get from Mathieu's scenario that everyone has the capacity to
talk, but no one uses that modality to communicate. Most people will
probably not even be aware that they can talk with their mouths and see with
Exactly. It's like a children (or anyone) that have never "heard" of a
signing language and sees one for the first time. 

Christophe: << easy to learn" for languages boils down to one thing, and one
thing only: *familiarity*>> 
I have read "Why Chinese Is So Damn Hard"
( and I agree with this essay.
My hypothesis is that it would be easier for Chineses to learn a language
with an alphabet than another one with different symbols for each concept.
Is their Chineses on the list that can approve or disapprove this? Anyway, I
agree that familiarity has a lot to do with the easiness of learning, but I
don't think it's the absolute only thing. Moreover, in creating a spoken
language from a signing language, the phonology will have to be created
based on no previous languages, so the concept of familiarity does apply for
that, but I don't think that means that all possible phonology these people
can chose will be equally learnable. 

Christophe: << There are plenty of things that are just not realistic in
this thought experiment.>> 
I think my situation is extremely improbable, but not physically impossible.

Christophe: <<And there is still merit to thought experiments>> 
I agree.