Hi there,
read this:
http://www.subsim.com/radioroom/showthread.php?t=184818
and this:
http://www.subsim.com/radioroom/showthread.php?t=176123
Currently Mega Mods are 'work in progress', there isn't a conclusive perfect mod yet (which I gather GWX3 was, though I never played SH3) but TheDarkWraith's (TDW) Mega-Mod (called Magnum Opus, or MO) is the nearest to perfection we have, though you'll need to get updates as outlined in the first link.
Saying that TDW is due to release a new MO soon!