Okay, it is possible to swap most weapon/armor through hex editing the savegame.das and you can keep the effects, or change them, but, you can't change the same item into more than one different item, because you're basically replacing the item globally. Unfortunately, the dragon blood armor has a different code that can't be changed to a normal one. If you have any of the dlc, the effects can be changed on, and with the reaper's cudgel you can replace it entirely with anything you want and have 4 enchantment slots.
Not sure what to do about legends items, and as for the resigner, yes it is a seperate tool, just called dragon age resigner. It's a long process editing saves for this game, but it can be worth it, just takes some practice, here's a link to the thread I learned how to mod this game from
http://www.game-tuts.com/community/f...editing-13332/