rigbyrigz,
Thanks for more confirmation of the WP being changed pre-ACARS report. Think I will still leave it as "apparently" though, as some data seems to be "confirmed" then debunked later when Malaysia decides to actually share the data instead of whatever they decided their theory of it was at whatever moment.
As far as your note - any system failure would have sent out an emergency ACARS. If the Transponder did drop because of a catastrophic event it would have. If merely turned off, I am not 100% sure. (but I think it would have) Hopefully someone else can clarify that last bit