That’s a good idea. I tried doing something like this in a one shot once as a test : Any PC or monster could voluntarily delay their initiative to anything lower than it currently is. It was a disaster. Very hard to keep track of and exploitable with spells, like you mention.

But restricting it to the first round and making it permanent…that might work.

As PC’s progress, falling to 0HP in combat gets less and less meaningful. So I have used a rule that whenever a PC is at 0HP at the end of their turn, OR fail a death save, they take a level of exhaustion. It makes the 0HP yo-yo more dangerous, and makes it so “death” has some longer term consequences.

I’ve got an Oath of the Ancients paladin in my group. I play it as if the thing behaves like a spell, we treat it as a spell for the purposes of this feature.

I don’t know how (I just signed up here earlier this week), but I’m willing to learn.