Supposing that a skilled Hemalurgist got hold of some a Shardblade or some Shardplate, how would he best use it assuming that the best way isn't to put it on and kill people with it.
That's probably the best way, to put it on and kill people with it. I'm not sure why a Hemalurgist would want one more than anyone else would because the metal is already Invested which means its not useful to him.
So there is no way that he could use a Hemalurgic spike to take some power from the Spren that's crafting it.
Oh, that's what you're saying. You want to grab something off the Spren? That's gonna be way harder than grabbing one that's not already made into something. So I don't see why he would want the Blade, just go grab it from them. Even then its going to be worse then, probably in most cases, a person. Maybe its possible that spiking yourself with a Spren would be valid, but you don't want to take it out of the Shardblade. That's gonna be harder, but you would probably have to go to the Cognitive either way to make it work, so yeah.