Not all KR are fighters, and many orders have bunches of Squires, who are formidable in their own right. I think it's been discussed elsewhere what the roles of each Order could be.
The argument isn't that one or two coins will crack Shardplate, It's that fifty or sixy of them will. Even a regular breastplate will crack
eventually, and without any opposing Coinshots, Kelsier can keep going for a long time.
I like it, but the Big Bad Wolf is more of a Koloss, I think.
She's probably Hoid's neice.
The real question is, what Cosmerical signigicance does the family (can't remember their name) have?
I think that your weight determines the max acceleration, not max speed. Heavier people can, in the same amount of time, make a coin go faster than a smaller person would be able to.
Remember, Steelpushed coins are comparable to gunshot. With wave after wave of coins, Kelsier could easily break Shardplate.
Not that it will be easy for Kell to kill the Storming Blackthorn!