A while back I created a properly segregated interface for turning message keys into messages. Since I've seen someone create almost the exact same thing, and now ended up needing such an interface in another project as well, I decided to put this into its own little library.
At this time, only msgText is exposed in the general interface, as this is the only thing I've needed so far. This can easily be extended for other use cases though. Just released version 0.1 of this library, which is fully tested, and is installable via Composer.
Hope this is of use to some people, and of great amusement to those who do not understand interface segregation and IoC.