I've been reluctant to comment in this thread because it seems that once again I'm the outlier in the group. Except for the OP who mentions the airspace restrictions east of PHX bravo in the report, I think I'm the only one who considers the bravo to be one of the factors in the proximate cause of this accident.
Here's my reasoning, flawed though it may be. In finance we have a factor for deciding if a segment of a large business is worth cutting or not. Without belaboring the point too much it comes down to a balancing of the segment margin of the offending dept vs it's cost basis to the overall corp. To take GM for example, the segment margin of the Saturn group was examined and found to be wanting. However, when we excise Saturn from GM as a whole, it results in a gross negative from the corp revenue, even though it was not producing as high as the Cadillac, or GMC segment. Nonetheless, it was producing, and the revenue stream was income that is now lost to GM where buyers may be out shopping for Nissan, or Ford, etc.
If we apply this kind of logic to the accident chain, eventually we get to a question; 'what would have been the result, if the airspace restriction to the immediate west of the mountain weren't there?' One may say that this isn't a valid question, but looking back at even a brief history there was a time when the bravo didn't exist around PHX, and VFR planes were not limited in climb except to the extent of the pilots discretion, and the machinery performance.
If we look at a profile of a plane enroute to some eastern destination from FFZ, and there were no restrictions on climb, it would be not only reasonable, but also prudent to perform the climb continuously from take-off to cruising altitude. Depending on the nature of the equipment, this climb could have been dialed into the VNAV A/P, or it could be done by hand. There would be no restriction sans the PHX bravo for anyone to stop us from climbing. In this case, the factor of having to maintain RH for a long time would not be a negative factor in the accident, but would be a positive factor in avoidance, because as long as the plane was heading north, it was still climbing. If we were also prudent, and requested FF out of FFZ as a VFR flight, we might get traffic notification, and possibly separation from ATC. Which begs the question, if a controller were to advise stop climbing for traffic separation, I might be inclined to report back 'cancel FF, we will handle our own nav, squawking 1200, good day'. Or, I might maintain current altitude, which would put is back in the danger box of potential ground obstruction. With the class B around PHX, this discretion or traffic call is reduced to an absolute limit by the airspace restriction.
It's my opinion, counter to many here that the prior restraint of the class B around PHX played a part in the accident. However, I haven't looked at the vertical profile to see of the pilot stopped climbing, and if so, was the reason he stopped climbing the result of not wanting to request a clearance into the B, or did he consider that getting a clearance into the B for a small corner of the time he was going to fly there more trouble than it's value, or possibly he might have considered that ATC would decline him that small corner of the class B, as he would be considered a nuisance? Without looking at the vertical profile of the flight, this is all rather specious I know, but if the limit was non-arbitrary, and proximate, we should consider that the pilot made decisions based on the fact that the class B did exist, and in it's absence a different profile would have been selected, that would have missed the mountain.
Having said that, this is not the single point of failure, nor is it a weak link in an otherwise strong chain leading to the accident. The fact is, the PHX class B does exist, and pilots have to deal with it, and the vertical navigation is the responsibility of the pilot. But - suppose in a world of 1988, there were no class B, and this plane, with this pilot, and this night flight were begun. Perhaps an instruction to remain on runway heading were given by the FFZ tower for separation. Would this have happened, in the absence of the PXH class B?