To add more depth to the techtree, perhaps add a stonecrusher like you see in mining facilities?
iron - gear - iron
iron - belt - iron
iron - gear - iron
Two parallel iron rollers you feed in ores of those minerals you do not smelt, similar to the current workings of the saw. Of course it would require both redstone and diamond blocks to be mined in stead of the end product, as it is now, but I think it will add something. As a bonus, you could reduce mining time on redstone, since there would be another step involved. It would be a more realistic way of mining stuff like this. Mine the block, take it home, crush it to get the end product. As it stands now, the only thing standing between you and diamond (pretty much the bee's knees of all materials) is your willingness to grind out shafts between layer 0 and 16. The only real downside to this is the lack of redstone before you get to this point in the techtree.