Like some people have already said, the origins were a great idea and well executed. I don't think that other than origins PE needs to take any ideas from DAO, mostly because PE will already have the best things about DAO(no morality bar, character skill determining success of combat, the PC will not say anything with out player consent, etc.).
They should learn not to....
Constantly compare the game to classics. While I greatly enjoyed DAO(it is favorite BW game), it didn't play like BG(2) and should have been marketed more on it's own merits
Not make a sequel that radically changes the mechanics. The combat system, dialogue system, and crafting systems were all changed quite a bit from DA, IMO for the worst. Please keep consistent mechanics throughout the series.
Not put too much focus on romances. While romances can be a good role-playing opportunity, if overdone they end up as shameless fanservice, which is what they ended up being in DA2.
Put cinematics ahead of gameplay content. I would rather play the game then watch it.