I understand where you are coming from, however if the axles coming adrift was a common problem on the Commers I expect the factory would have addressed that issue at the time to stop it from happening, rather than leave the problem and just relocate the hand brake. If the axles coming adrift was a common problem we would all know about it, they've been on the road for 50+ years and people always remember things like that. Here's 2 easy examples, if I say Triumph Stag, just about everyone with some interest in cars will reply Overheating issues, and another, Fuel-injected Triumph's = Vaporisation issues. These problems were sorted out years ago, but everyone remembers the bad old days.
I just think we need to be conscious that our vans are getting quite old. The lock nut arrangement that holds the axle in place was most likely fine for traffic of the day, unfortunately as it can't be seen it's most likely never been looked at since the day the van was built. When you think about it if the split pin fails on the front hub the same thing could possibly happen with the front wheels. That's one of the benefits of disc brakes, if a bearing fails or the retaining nut somehow comes loose the calliper holds the disc in place. It may flop around and do some damage to the calliper and/or disc, but will hold the wheel and hub in place until you stop. Think it's just something that should be on the check list these days.
My thinking on the hand brake relocation is that it was moved to the front wheels for a couple of reasons. Firstly cost, as the cable is extremely long and suspect by moving it to the front they may have been able to use an existing cable off another Rootes vehicle. There's also the issue of cable stretch in a longer cable. Seizing and possibly freezing in winter may have also been an issue, I know my rear cable isn't like the modern plastic sealed/coated cable and was seized in place when I got the van. Secondly there is more weight over the front wheels in a standard Commer van, particularly the utes and the stripped down versions going out for Coach built bodies. This may have been considered a safer option for when a Commer was parked on a steep incline on some kerbside slushy snow, or even just trying to hold it in place on a car transporter so the driver can get out to tie it down without it sliding down the incline.
Just my thoughts on the matter, something for you to chew over at Commerfest.
Cheers Stephen