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I would have thought that best engineering practice would have been to fit a solid tapered pin rather than a plain cylindrical pin. Some distributor drives use a tapered pin which can only be removed and reinstalled in one direction.

I suppose pin failure, in addition to incorrect pin type and fit might be attributed to long term use of excessively high viscosity motor oil which can place extra strain on the entire oil pump drive system including the drive gears.

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Not a bad idea. A nice discreet out of the way sensor in one of the ports at the rear of the main gallery to work your light. The headlight on the wheel might interfere with seeing the speedo so it could lead to a ticket but a nice red floodlight under the dash might work as well. In my case it probably wouldn't hurt to add a klaxon too.

Along the lines of the headlight on the steering wheel to grab attention. Did any mfg ever do something along the lines of combo instruments and idiot lights?

I vaguely remember reading an article in the 50s or 60s when fiber optics and light pipes were coming on strong and all the how-to magazines were dreaming up or in some cases documenting uses. One of the illustrations was a combo gauge. The car had instruments but when a problem occurred, to get the drivers attention the whole face of the gauge turned into an idiot light by virtue of a light pipe channeling the red light into the plastic face of the gauge.

Can't remember if that was an actual or fanciful way to use the light pipe. I know the color changing speedo needle or indicator was used by many including Packard but how about instruments.

For fear of incurring scorn, I have always been a silent fan of idiot lights. After the initial vetting of an engine that is new to me, I don't care what the oil pressure is. It is an extremely safe assumption that the oil pressure will remain OK unless something catastrophic happens--like a pin shearing, or a fitting cracking as happened to me this very morning. In a good running car on a long drive, the chances of me noticing a sudden oil pressure drop are miniscule before the rods begin to rattle.

According to the reliability experts, things more often fail in the beginning or near the end of life. This is plotted in a Weibull aka bath tub diagram.
One can only speculate as to causes without post mortem analysis, but when things are rebuilt they sometimes don't get back to full specification for tolerance either thru wear or interchange of parts for availability. One of the key indicators in troubleshooting failures is, was anything changed? It appears there possibly was more than acceptable slop in the pin connection which led to fatigue cracking. Substituting a harder pin might have made things worse in that regard. You don't re-engineer a issue when it's out of specification as cause. We should recognize that the early parts may not have a long service life time as designed as the state of the art was still improving. People tend to associate Packard with fine engineering but I'd say they probably blew a few and used other company's parts/designs as well.
"Idiot" light can better be described as "cheap" indication. I personally think it a misapplication where gauges are more appropriate. If you don't test warning lights occasionally, it might fail on demand, and you'll have the same outcome. Especially true for the old filament type. Some newer cars light up all the dash on ignition for this reason. For this reason, it's actually better to have a light on (green) in run condition, then change to red/yellow, than to only come on(red) to indicate fault.
A gauge sends information all the time, even when off, so is more useful and fails safe. If the gauge goes out, it won't respond when it should, so you know somethings wrong when its wrong too. It may not indicate what the failure is or where it is occurring, however.

The best defense is an ignition cut out or kill switch triggered by oil pressure.

Some small engines, i think Kholer, runs such a switch and other variations of ignition kill switches triggered by oil loss.

I've said it before and i'll reiterate:

NOT just the vintage car hobby, but ANYTHING that requires maaintenance is now grossly plauged with poor quality replacement/service parts. THe problem has compounded over the last 8 to 12 years.

This roll pin breakage is uncalled for and a direct indication of poor quality control. A problem i've recenty had even with well known long time household name brand parts. Literaly even with the kitchen faucet in my sink at the house.

As I've mentioned before, tapering is usually done/required for centering parts along an axis.
A straight pin can also act as a shaft to attach moveable parts like a lever or act as a shear pin to limit torque. This is not the usual role of a tapered pin.
Role pins are a later invention, circa '48, and are meant to be self retaining. The spring force holds it in place. But as I mentioned, if there's movement due to wear, etc, that places the pin in a condition for fatigue of the spring steel.

Maybe Mr Phils38coupe can save the roll pin for analysis.
Maybe take a file to the roll pin to see how haard it is or isn't compared to a KNOWN good quality roll pin.

If you look at Mcmaster Carr site they have roll pins and better grade which are mil Spec which is almost 1/3 stronger than standard pins. Another area to check would be the sizes of the hole if its worn the pin would fail sooner due to the impact from warn parts . Oil pressure cut off would be a good backup easy to install and good cheap insurance