Alright, I’ll just say it: killing Sprucecaps is bad. There, I said it.
Regarding your concrete suggestion, I think your idea would overly limit PvP. There’s no reliable way to distinguish between a genuine Sprucecap and an alt account. To make it work, you'd have to restrict general crimes as well—and even then, there are plenty of ways to mess with people that don’t technically count as crimes. Also even if your solution is implemented you can just maintain a low Credo level Character that then still can kill noobs with impunity or you dont allow people without the credo or low level to kill in general, which just makes that credo mandatory for anyone who doesn't want to regularly have to remove the Windmill of tolerance, paved with coal on or near their property.
Why shouldn't I have the right/ability to kill that Character? I don’t see how your suggestion effectively addresses these longstanding concerns. None of the proposals so far have been convincing enough to solve the problem. I would if I was you try to adress those objections. Just look at that horrible
"Holmgang" Thread to find a few, or the
"Developers Thoughts on PVP" Thread.
Could be that due to poor reading comprehension on my part I actually didnt get how you adressed these things, or I misunderstood something, but if not you should flesh out your idea more.