Thanks for putting this out there, Amon...
1. Maybe consider making the 2ndary metals copper/tin or iron (would keep us from setting aside an extra silo, too :) ) Another consideration might be taking nickel completely out of the game (this addresses jerko-s idea as well (which i personally like).
2. Bronze ore shouldn't be too confusing of a change - and might work easier in the minds of a noob, anyway (ref: knossos' above mentioned experience)
3. Ask me again in a month after I'm back into the swing of things here ;)