I do remember thinking that Shen Wei's pendant had to be one of the Tools that he was hiding for some reason

Well, now that would've been fascinating. Cursory thinking doesn't really get me any reason why he would that doesn't go very AU, but the thought of already overpowered Hei Pao Shi also having access to one of the hallows all the time? Well, you could do stuff with that, is all I'm saying. Or perhaps it's more of a 'sentient hallows' situation, where one of them chose to attach itself to a newly reawakened Shen Wei for Reasons.

... Don't mind me, my brain is just running away with me again, apparently.