We should be focusing on saner bash defaults, since it's the most common shell in use.
That kind of work is not glamorous and highly controversial. Ideally there should be some sort of cross distro/OS working group (Debian/Ubuntu, Red Hat, SUSE, FreeBSD, NetBSD, OpenBSD, Mac OS X, etc.), similar to the working groups that standardize the web, where such proposals can be made, voted on and adopted.For example there should be no reason in 2016 why a sane solution can't be found for having almost every bash installation recognize all keys on the keyboard (i.e. arrow keys wouldn't produce ^A sequences or similar).
Another thing that would be sorely needed but would involve a much higher volume of work would be a template, at least for all GNU utils, which they use to define they options, parameters, arguments, whatever. And by "template" I mean library, actual working code they could include and configure.
Instead of each shell (bash, zsh) having to come with a million small scripts that configure auto completion, these shells could just query the standard-compliant tool for its usage and would receive a standardized reply with everything. Powershell has something like this and it is a great idea.