You've given me a horrible flashback to the time I took two hours to figure out that some code wasn't working because someone else's copy/paste had, somehow, introduced a few zero-width spaces that I did not think to check for

But yes, I agree that using just one character for all three of those would be fine for general purposes and easier in specific fields. I think I'd prefer the en dash to be the default since it's the middle ground size, but to be honest as long as we don't need to start using em dashes as hyphens for very—wide—compounds I'd be happy