Redmine

I'd like to customize just the vocabulary that Redmine uses for english (change "issues" to "tasks", etc).

Is there a preferred method of doing this? I can think of three off the top of my head:

1. Edit the en.yml locale file: I think this is the simplest. But I don't know how "sacred" that file is (i.e. should it be changed on an instance-by-instance basis, will it get updated if I update Redmine?) Is there a place I could put my own edited version to override it instead of editing the actual one?
2. Add a "custom" locale file: By "custom" I mean something that's not a real language, but more like cust.yml. I've tried this and it works, but there seems to be some quirks, including error messages in the preferences and non-translated emails.
3. Change all the views to point to different entries in the locale file: I think this is pretty obviously not the correct or easiest choice, but it's a choice.
4. Perhaps some sort of CSS replacement magic?: I don't really like this option either, but it does avoid messing with the source, configs, or plugins.

Any help would be very appreciated. Thank you!