The Current diamond system revilves around using large amounts of coal to make one, measly diamond. However, In the real world, it doesn't work this way. It uses extreme pressure, and heat to make diamonds. the system in place right now uses alot of macerated coal. In order to apply such large amounts of heat, pressure and other things, I suggest something similar to a coke oven or blast furnace to make diamonds. It would use significantly less coal, and no obsidian or flint. Of course, to prevent abuse, this process would take a very long time, and be very expensive to start. Ideally, the entire thing would be 5x5x5, and run on EU. It could be treated as one block, or not, I have no idea how difficult that may be to code. If not, It could be one, single block, just like a compressor or a furnace. It would potentially use advanced machines in it's crafting, looking something like this.
= Furnace, electric or induction
=compressor, singularity or regular.
= Mass Fabricator
** it's so obscenely expensive to make sure it's not overtly abused, and requires a long term commitment to pay off.
It would have the regular GUI of a machine, but 4 pieces of macerated coal would go into the top, or pure graphite.
It might take a full mincraft day to complete one cycle, or more, Idk. Either way, I think it's a cool idea, and I hope you at least consider it. Thanks.
Here's a few articles on it... Maybe a secret recipe involving IC2 rum?