I have a hydraulic front brake, made by Lew Walwork. As far as I am aware, there has not been any issue with these, I had to renew the slave cylinders over winter and taking the brake apart it is a fantastic piece of kit! As I only did about 500 miles last year I cannot speak for the longevity from personal experience, however, I know that many bikes use them, and the one I have belonged to a prominent club member who did many a mile with it.
The linings are off the shelf for a mini, which means replacements are easily obtainable, and very simple to change - and it removes the issue of non rivetted linings from unglueing themselves from the shoe.
I'd post some photos but the brake is at my dads at the moment in need of a part.
From what I can tell, the design seems to remove stress from the original brake plate, transferring to an alloy disc behind it, so it looks authentic enough, and should stop all of the above fears.
Since this is becoming a topic of conversation, perhaps we ought to look in to whether the club would like to fund having some more made up if Lew agrees? I don't know if he still makes them for people?
AOMCC Member Number 4068
1957 Ariel VH