EzekielRaiden
Follower of the Way
You say "rarely relevant", but one of the few things even most haters of 4e liked about it was the Bloodied condition because it was useful. Creatures that gain or lose benefits while at or below half HP. Features which become more powerful at half HP. Transforming "boss" monsters. PCs getting a reminder that they're less sturdy than they think. Etc.So here's the problem with what you're suggesting.
You want to use the Bloodied condition to trigger a creature feature. You then want to be able to impose the Bloodied condition under special circumstances to make that feature more threatening. So you hit a PC with an attack, they fail a save and are now "Bloodied" without being below half HP—
—oh, and now they're regenerating HP up to their maximum, because they have a feature that allows them to recover HP each turn when Bloodied and is meant to only be able to heal them up to half HP.*
There's nothing that couldn't simply be written as "if creature is below half HP" rather than introducing a rarely-relevant keyword for such, and you can't do something that imposes the Bloodied condition under abnormal circumstances that doesn't consequentially trigger other effects tied tobeing Bloodiedhaving the Bloodied condition and normally balanced around the typical circumstances of the condition.
*But to be frank, given other changes to the rules and features/magic items to allow egregious exploits, it wouldn't surprise me if something like this eventually became possible.
You dismiss it as near-useless. I've seen how useful it can be in action. Have you, in fact, actually played with it?
Or are you, to use the term so many people love throwing around on here, merely complaining about it in a white room without any actual experience with it?