I thought locale is mostly controlled by the environment. So you can run your system and each program with it's own separate locale settings if you like.
I wish there was a single letter universal locale with sane values, maybe call it U or E, with:
ISO (or RFC....) date time,
UTF-8 default (maybe also alternative with ISO8859-1)
decimal point in numbers and _ for thousands,
metric paper / A4, ...,
unicode neutral collation
