As someone who can't stand the gambling elements the devs added due to WoW (I said WoW since I can't help but assume that after reading this: https://factorio.com/blog/post/fff-438), I have mods that give me quality without the need of gambling. The best exemple is Steeper Quality where I can set the quality level of Common items, aka I don't even need to touch the WoW (or similar) game's quality that are behind itemlow % chance + recycling until you "get lucky". On top, no need need to set filters for each quality, change filter, replace everything lower with higher, create recycling and upcycling, bla bla bla bla, because all quality are the default normal ones and have good stats = can enjoy the quality elements from DLC that I paid for without gambling

So, after all that, I hope I explain why the "have items as ingredinds for quality" is not an issues, and insted, I would love to have the option to have all items from molted iron and/or chopper. Just like how you made for engine unit and space platform, but same for: storage tank from melted iron; having all belt related using melted iron <- Since lub is also needed, I guess no melted chopper; pump; and so many more items (aka more then you added) be crafter from molted chopper and/or molted iron would be awsome.

2 Exemples to hope to clarify any confusion I caused

Electric engine Unit: 1 pipe with lub, 1 pipe with molted Iron (since all are iron related) and since there is no 3rd pipe entry for foundry, separate green circuits (<- aparently they are know to some as electronic circuit, what wierdoes, even googling factorio green circuit will bring up the green circuit wiki)

Pumpjack: to be crafted using molted iron and molted chopper exactly because there is no 3rd liquid type needed and all ingrediences are chopper and iron based.