have you heard of the salary cap? it's a new thing. it means, unless oel or hughes is traded, the canucks are not wasting assets or cap space adding a valuable left hand defenceman. for different reasons a trade of either is unlikely so, for better or worse, they already have 45 minutes per game and $14m per year in cap spoken for on that side for years to come. they have 15 minutes to fill spending about $2m in cap space.
they could certainly make room for a solid young elc prospect over there, but they would not use valuable treasure to pay the premium for a known marquee prospect like byram to fight for minutes at the expense of sunk costs. they will logically use that treasure to strengthen themselves elsewhere.
and you don't ever make a trade based on the hope moving your best player to the right side to make room for him will work out long term. hughes is an undersized defenceman just now finding a way to play defence on his strong side. committing to a major move based on the belief you can safely put him on his backhand without a drop off in play would be idiotic.