I have a requirement to display the users' 'real names' - the ones they enter in their profile - rather than their usernames when one views posts or post lists or user lists.
I have done it, and it's quite a number of smallish changes, so it would be nice if it were in the standard if only to save me from having to reimplement it every upgrade.
Is anyone interested?
I have not made it 'switchable', but it would be trivial to make it dependent on a setting in config.inc.php