I'd like to see all mods from resonant engine, not just MFFS and Powersuit.
Tesla coils, mechanical generators, EMPs, antimatter missiles, genetic modifications and more..
I also used Bibliocraft a lot, shelves are pretty useful IMO, Powersuit looks even more cool on armor stand.
Already mentioned:
Mekanism
I enjoyed it quite a lot for it's chemistry system, so I would definitely go for it.
ModularTurrets, Natura
looks amazing, I'll try them.