Like you, I would bank (say 45º) to reduce negative Gs... in real life.
And get off the airway
The passenger oxy lasts for 13-15 minutes. At an average rate of descent of 6000 feet per minute in an emergency descent it takes you just under six minutes to descend from 40,000 ft to 10,000 ft. Maybe eight minutes at the worst. A gentle push over is all that is needed once you decide to get going down. There is little point in going into a 45 degree angle of bank (and risk getting into an unusual attitude in IMC) just to avoid negative G when there is no hurry to descend based upon passenger oxy time limits. If you need to turn off the airway (and watch the new en route safety altitude) it would be safer in the long run to make a level turn and when on desired heading start on down. The 45 degree angle of bank caper has been around for years but it is rarely justifiable.