I'm going to preface this with :
Your idea has merit and I have nothing against it should SE decide to make it available for people to do. It impacts me literally zero amount, and logically I have no arguments against this being put into place.
that being said (lord, how many mean things start with this) , your only real argument against using what's in place is your own brains hangups against having stuff you've "earned" on your old character, on this new character. If you really want to experience the adventure again, running the story from 1 to 70 on a brand new character should fulfill 99% of your criteria. That stuff is still there, will always be there on your old character and should you really want to continue the new characters "story" once you've gotten your alt to 70 or whatever goal you set, you can fantasia your old character and continue the narrative in your mind.
to sum up: the experience is available to you within current game options and overcoming your own hangup will probably come before SE implements a solution for you.