I don't see the problem with including the option to choose difficulty in the next game. The series already has the mechanics for difficulty settings. Demon's Souls has world tendency and Dark Souls has rising difficulty on subsequent playthroughs. Players can interact with each other regardless of what "difficulty" each of them is under.
As you can likely imagine, people can and do take advantage of this. Some Dark Souls players will camp in an area on a higher cycle and use NPC phantoms or Undead Rapport (particularly when under a Gravelord Servant's curse) to beat low level invaders. All you'd really have to change to that formula is give players the choice of which cycle they start on. --- "Every inscription, every utterance, every gesture seeks to dominate the plain of meaning." Chad Dumier, Deus Ex
Why can't everyone just accept that people like what they like and stop acting like their opinion is universal truth?
I don't like the Souls games, but that doesn't mean I don't think they're great games that a lot of people love. --- Day One buys for 2013: Devil may Cry, Dead Space 3, GoW: Ascension, Bioshock Infinite, The Last of Us, Grand Theft Auto V