So this is where you can put any missed oppotunities, that IN YOUR OPINION would have improved a novel/worbuilding acspect.
Here's my first two
So we have Pewter,
in allomancy it increases strength,
In feruchemy it stores strenght
then along comes Hemalurgy, and you find out one metal steals physical strength, and you think to yourself, "Huh I bet it's pewter,"
Pewter: Steals physical feruchemical powers
Why Brandon? Why? you had one job, one theme for pewter, and you give the ability to steal physical strength to Iron? it's not even the base metal for pewter!
At least you got Tin right.
Chromium and Nicrocil,
these are just Aluminum and Drualumin, but to other people, they don't even change that much, none of the other metals behave this way except Atium and Malatium to gold and electrum, but those are Shard-metals, not base ones! you could have at least made them AoE's that forced or prevented burning of metals.
Anyway what where your missed oputunities?