Right now, if a fort doesn't have a metal you're not doing much with it. No matter how much you request you won't be seeing more than a couple of dozen bars on a caravan of all sorts. Since in a standard embark you don't know which metals you get this is extra frustrating. So I want to be able to get access to a few metals of my choice with a little bit of gameplay.
I haven't delved deep into how mods like Masterwork do things, but I think the following ought to be possible by analogy to some of their workshops:
a) Catch a leperchaun. Maybe the loathsome little things play in your biome, maybe a trade caravan brings them. They should be pretty broadly available though no doubt expensive. I imagine they would be tricky to catch in a trap. The legends say they can open a way to a secret pot of gold, which we suppose is more or less true...
b) At a trap works, you would be able to "create a leperchaun portal obelisk to XXXX". This should be a large redoubtable furniture piece carved from stone, studded with at least three mechanisms to control the verniers, maybe a couple of large control gems glow ominously etc. The caged leperchaun should be consumed in the process (if the game can implement that), as part of the deal is that it gets to go free through the portal. There should be a list of labors (perhaps in a submenu) for different values of XXXX. Simple metals like zinc and tin have 100% success rate. Platinum, aluminum and such have lower success rate. Adamantine has a pretty low success rate and other problems can be specified in the ensuing reaction... Failure indicates that the leperchaun went back on its word, tricked you, get you to let it through and then the portal blew up or something.
c) You build the leperchaun portal obelisk to XXXX. Wherever you put it, you have this thing sitting next to a big platform over which a ball of rock hovers (which is roughly the radius of a leperchaun, since it escaped through this hole). The rock is actually Somewhere Else Far Away With The Metal You Want. Someone with mining skill can work at the shop, goosing the verniers this way and that to bring ore into the chosen region; they can then strike it with their pick (at least, I think they should use one for style to physically break the ball from its remote moorings, though I suppose they could just hit some button) and the lump of stone is produced by the workshop. Ordinarily this should be very safe, but if adamantine is being sought there should be a good chance of producing a non-tame, non-caged Fun Monster along with the rock, if that can be implemented. Also an even better chance of magma mist emitted. For dorfs who have used up their adamantine, this is a small price to pay...
d) Another option at the portal to XXXX should be simply to mine the base rock. There might just be one base rock pre-set as a reaction for each type of portal to XXXX that can be built. This isn't all that useful but it shouldn't take much extra effort; it's just an alternative to mining the ore.
e) One last option at the portal to XXXX should be to "lose an item in the portal". Just about any object should be eligible to be taken and placed into a void space such as where you just mined an ore stone. (A few objects might be too big or problematic code-wise, like a caged noble) The idea is just to be able to get rid and I mean totally rid of FPS-robbing trash you have lying around so you never see it again. I imagine it looks like you crack out the stone from the ball hanging in the air, you then turn the height vernier down just a little until a shell of rock appears at the bottom of the ball, you dump your stuff into the shell, and then you move well away.