Yes, I am assessing his chances of complications, and I don’t have ‘a number’ because ‘a number’ does not exist, only the probabilistic ranges that we have from the medical literature. I do know he is clearly over 30, possibly over 40. The odds of nerve damage vary per study, but are high, as high as 100%, most likely much higher than his odds of developing sleep apnea (what’s the number there?) Most complications have a higher probability of occurring the older the patient. The rate of dissatisfaction for this procedure is higher among patients seeking solely aesthetic benefits. I am directionally correct here. He’ll have to do his homework if he wants greater precision, if he feels that matters. I feel satisfied having shed light on what for him might be unknown knowns and unknowns.
The aesthetic effect also suffers from some degree of unpredictability. The soft tissue changes around the nasolabial area largely unpredictable, with nasal widening of some degree very likely if not guaranteed. This isn’t to say Gunson’s plan isn’t a good one, just want OP to understand this surgery isn’t flicking a light switch, as the vast archive of dissatisfaction on this forum and elsewhere evidences.
I'm sorry BUT some of what you're saying here rings patently incorrect to me, in particular the statement that 'odds of nerve damage are as high as 100%'. I liken that particular statement to saying the 'odds' of winning the lottery are as high 100% . Sure, a person who won it might think that but an isolated outcome to one or a few does not reflect the 'odds' or probability assessments of the occurrence.
ETA: As to odds of damage to mandibular branch of nerve, I agree that those are higher than some of the really extreme risks. Although I don't have the statistical probabilities at hand, that particular risk is certainly something to inquire about with the doctor as to some feedback of what it is in his hands vs. one's particular circumstances.
With regard to a patient experiencing a particular risk associated with a particular surgery, EMOTIONALLY, the 'risk' is 100% to that patient after the outcome occurs. But that is not a statistical predictor of any one other particular patient or patient population as whole.
For example, the lottery exploits IRRATIONAL thinking where they get you to think in terms of winning. But in terms of a typical example where one uses the actual probability of winning multiplied by the financial pay off and compares that to the cost of a ticket to take the chance, the EMV (estimated monetary value) of taking the chance (1M) is about 1/13th of a cent which would be the break-even point to pay for a lottery ticket (as opposed to the $1 cost). Point being is there are more irrational thinkers than rational and that's how the Lottery itself is always the winner. Can go the other way around with Alarmists and Fear mongering where the focus is on losing (bad outcome). Promoting that sort of thinking has nothing to do rationally going about taking a risk under uncertainty.
As to his doing his 'homework', I've already given him some advice, in particular having to do with the science of Risk Analysis and decision making under uncertainty, I've already suggested he look into that. I would suggest you do the same. It is an extremely rational field which deals with such things as 'risk aversion' when justified and when irrational, using probabilities in taking a calculated risk. In short, there is a highly RATIONAL way of thinking involved with decision making analysis.
The only 'absolute' here, if one is in pursuit of absolute 'certainty' (100% certainty) is that no surgery at all will bring the risks associated with surgery to 0% which appears to be your assessment here.