Regarding your concerns about wands being already strong and therefore shouldn't be buffed anymore... I mean, bow builds are also super super strong. Just because they're (currently) strong doesn't mean their mechanics shouldn't be changed to make more sense.
Agreed that relics shouldn't be able to be "created" by a trader from a legendary item, but I do think being able to trade one relic for another would be reasonable. Or, if the devs would prefer otherwise, the next best would probably be to prevent them from being tradable entirely.