Marble is probably the best layer stone to look for. Not only can it hold sphalerite and tetrahedrite like the other metamorphic stones, it also can contain malachite. Phyllite, schist, and slate are other options; while they can't have malachite, they only have the vein stones common to all metamorphic rocks, of which there are 3 (sphalerite, tetrahedrite, and cobaltite), 2 of which are useful for you. If you get 2 vein types in a metamorphic strata, if it's marble you might get duplicate copper ores, but in those 3 you'd be more likely to get both of the vein types you're interested in.
Also, you should note that reacting two ores together does
not produce extra bars. Reacting a sphalerite and a malachite to bars, then reacting the two bars together, produces two brass. Reacting a sphalerite and a malachite to brass directly produces two brass. You in fact
lose bars if you use tetrahedrite, as reacting a sphalerite and a tetrahedrite to bars and then the bars to brass produces 2 brass and 20% of the time also 1 silver, while reacting the sphalerite and tetrahedrite to brass directly produces only 2 brass.
This assumes, there is no preference or schema in the engine for placing ores, layers, and minerals. Civs have preferential biomes... why can't other things? Removing something from system like this won't break it, just the next preferred items will fill in the places. It also leaves room for exceptions due to noise in how the stuff gets placed. Either way allot of assumptions are made about how this stuff gets done. I haven't seen any !!SCIENCE!! to make me believe either way.
It's not that other things
can't have biome preferences (except that minerals are generated before biomes), it's that they
don't in this case. World generation order goes elevation - temperature - rivers - lakes -
minerals (rock strata) - vegetation (biomes) - wildlife - history. Some things do happen to coincide more often (such as sedimentary layers and swampy areas) but that's not "intentional" so to speak (in that case, it's because sedimentary layers happen where rivers are predicted to have run, rivers lower the land, and low lands are more likely to be swampy).