I'd like to see the justifications for some of these, particularly 3.5 which I see as only obscuring that the current context is a function.
Major disadvantage: in the short term it might be difficult to parse.
Possible additional major disadvantage: programmers may never adapt and find it difficult to parse for ever more.
For visual parsing, consistency matters. In an object literal dec I expect:
name : value
That's easy to parse visually. Not good is when suddenly we get: nameandvalue(){
in the space that our brain expects the former.