add a socket to any item
More interesting things to add to sockets
ability to modify affix on items ("imbuing"), could require materials to make it harder/more expensive
MUCH greater variety of affix type. Things like "reduces all cooldowns by 10%" and other stuff that's useful for any class - not just primary stat. LOTS AND LOTS more unusual and strange affixes. There are some legends with good ones, but there's only a few, and those should be able to roll on non-legendary items. USE YOUR IMAGINATION BLIZZ!!!