But that means you'd need to be constantly building new smelting facilities as local wood resources were used up. Making charcoal needs relatively little infras

But that means you'd need to be constantly building new smelting facilities as local wood resources were used up. Making charcoal needs relatively little infrastructure, so it'd be easier to make and transport. I suspect the optimal answer is a combination of approaches. Build a few foundries distributed optimally near large forests, cut timber and char it and bring the charcoal to the foundries. Maybe cycle them on a 40 year basis so you can re-seed the forests and grow enough timber to make them worth it.