I agree. Those would be the points with most impacts. However, the outcome would be quite far away from standard JSON, so we would really be talking about something like ASON or SDL already.

There are some beginnings like this one:

http://json5.org/

Here's another, that supports tables:
https://github.com/krisnye/ion

Unfortunately there doesn't seem to be any decently popular winner of the 'extended JSON' language, apparently most are fine with just adding comments.  YAML might be a choice, but I find it diverges a bit too far (and I'm not a fan of significant whitespace).