I didn't need to do any requests; after a while thanks to automation I had more resources than I knew what to do with, even crafting the end-game coin resource was no big deal. Unless I'm missing something by not doing the requests?
Including the coin in the Furnace was a last minute change. I played through the game multiple times and I thought that players might get frustrated with the devils balancing and I'd rather have players play through the game instead of giving up midway. In the future release I'll rebalance the devil. :) Thank you for playing!