GregTech is a highly controversial mod that does two things: it changes a lot of recipes to make a load of stuff harder to make, for example blocks of metal have to be made in a compressor instead of just crafted, and macerators need diamonds instead of flint (I think), and also adds a load more machines. It disables the basic Mass Fabricator and adds its own Matter Fabricator that takes a load more power. It also adds some higher tier generation and storage. The recipe changes can be turned off in config, so you can just use it for the additional machines, but none of the FTB packs have "easy mode" config by default.