I love my magma forges. So I had an idea to create magma extraction facilities which would provide magma bins.
That would be useful, though I'm not sure whether that would be very realistic or if the game would support that. If custom workshops can produce magma, you could make a magma powered workshop that turns several stones and a magma safe box into a magma container, which can be used at another workshop to make some magma. It would be tough to make caravans offer them in trade...maybe it could be a seedless noncookable plant that only grows on mountains?
The way I was thinking it, the magma extraction facility would be a workshop that needs to be placed over magma, and makes a magma safe box into a "magma bin" (which raw-wise is just a craft or something). On the other end, you use your stones and blocks, plus a magma bin to create a magma bin forge. This workshop allows you to forge metal items without the need for coal or magma.
The only place there would actually be magma involved, code-wise, would be in the fact that the original workshop needs to be built above magma. And I seem to remember it has been confirmed that there will be a tag for that.
The above might be a bit too easy, and I'm considering that I might need to either make the process magical somehow (maybe the magma bin also requires fire imp bones), or maybe the bin gets used up, making it, in essence, super-coal.