Inspired by the "withJS-url parameter"-script floating around various wikis (which calls importScript() if the passed pagename is in the MediaWiki:-namespace), I think such functionality would qualify as core functionality.
For backwards compatiblity and to avoid any security issues on wikis which use the MediaWiki:-namespace on a less-than-sysop security level, this should be disabled by default, and enableable with a wiki global (eg. $wgAllowWithModuleLoading=true;)
However given how the resourceloader currently works and how it will/may work in the future .
I think it's best not to implemenent the script as it is now on those wikis, instead I've made this bug depend on bug 27535 ( registering wikistyles and wikiscripts as part of a module ), and propose to make the parameter someting like withModule.
That way it can be used to load CSS as well, since CSS can be (part of) a module.
This also stops the need to create mini-scriptpages in the MediaWiki:-namespace that would call importScript() and importStylesheet() several times (once for every css/js part of the module) in order to make it work with the withJS-hack.