hmm ok.
first off I do like the idea of the spearhead of the Spear of Destiny being the knife and maybe giving Harry and edge kinda interesting. could also be why Nico wanted it. with that and his noose he would than become pretty much unstoppable.
now as to the Bodkin and vault blade.
sorry but I do not see how or why the Bodkin would be in the vault at all. it is in Mab's possession. another thing, the items have to do with Christianity, the Bodkin does not have anything to do with it.
Changes the blade is a bronze leafhead blade with a wooden handle wrapped in cord and leather.
SG the blade is a leafhead blade with a wooden handle. no mention of cord or leather. you do not go around altering relic of power.
Changes the Bodkin had a bloodthirsty feel to it. "energy surged through the little blade, power that was unfettered and wild, that mocked limits and scoffed at restraint. not evil, as such- but hungry and filled with desire to partake in its portion of the cycle of life and death. it thirsted for bloodshed." that does not sound at all like a holy relic.
SG when he scans the objects he relates their power to Amoracchius, a holy relic. when he touches the knife he would recognize the power. "even that brief contact was like touching a live wire. tingles flew up my arm and set every hair of my body on end." does not sound like the blood thirsty effect from the Bodkin, but from what he has felt previously from Amorachius. GP ".. it fairly hummed with power, vibrating in my fingers." than later, "something that hummed quietly, a silent vibration of power that ran through the plastic and into my hand. a vibration I recognized." "still, it buzzed with that quiet, deep power, at once reassuring and intimidating."
when Harry states that the bronze hilt clicked against his brace, I have to believe that is an error. since the handle was already described as a wooden one. hilt- noun, the handle of a weapon or tool, especially a sword, dagger, or knife. syn. handgrip. I think it was meant to be the crossguard or pommel that was bronze and tapped his brace. which seems more likely to hit the brace than the actual handle. unless the error is the handle description. in which case it is still not the Bodkin.