I actually found that the super wide stance was a bad idea for me and had more luck coming in to about 18" between my heels, but that may be entirely down to body type.
I'm thinking, sumo deads, normal deads, zercher squats, sldls, deads stood on blocks or with a snatch grip, RDLs and of course GMs would all be excellent assisstance work. Of course ultra wide stance squatting would also help with the depth issue.
combine some of those with a decent stretching regime and you should be in the money.