If I was just hired as game director of D2 I would introduce the D1 main quest of finding and killing the black heart, with different starting points Humans would start in Cosmodrome, like current, and need to fight through the Devils to escape to the Tower, aided by Shaw Han Awoken would start in the DC, fighting through Taken,Hive and Scorn to get to the Tower, aided by Petra Exo would start in Europa, having to fight through Vex to get to the Tower, aided by Elsie All 3 origions will converge into the same quest once you get to the Tower Awoken will get exclusive dialogue when negotiating with Queen Mara and Uldren , Exo will get exclusive dialogue when talking to the Exo stranger