I don't know if this is possible but why not let players keep the items they get and reset the levels. I find it to be a good solution. ( I mainly would like to keep my legendary gear from the iron banner that would effect the gameplay because it is cosmetic)
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The only things i would want to keep from the Beta would be Iron Banner stuff and Class Gear like cloaks and Emblems, The rest doesn't matter in my opinion because we will get better gear later anyways.