I'd propose Looch for Bobby Ryan (10% retention). Ryan has one less year on his contract and - while equally inconsistent - provides a considerably higher level of skill than Looch. For the Sens, even with the retention they end up paying less actual money vs keeping Ryan (over the course of the 4 years of Ryan's contract). The trade would take place after July 1st (where both players are paid out their bonus, Lucic being the larger bonus.
Looch remaining contract (after bonus paid this year): 3.5, 6, 4, 5, 4 totalling 22.5 mil + 2.8 mil total retention on Ryan for 25.3 mil but have Looch for an extra year (essentially like paying Looch 100k for the last year).
Oilers end up paying 25.2 mil for Ryan.