So what’s wrong with kg for weighing things, st & lb for people, miles for driving distance, metres for building things, C for temperature and feet for ascent of hills and stuff?

What’s right about it?

But I love what you’ve done with ‘half-four’ to mean 3.30. I really enjoy doing that with my German colleagues.

That’s not exclusively german though as germanic languages in general and some slavic languages use this format.