An updated Colt New Service in 44 Special or 45 LC would make an outstanding self defense revolver. I don't have a picture of one of my New Service revolvers, but here is a vintage ad:
Compared to the monsters of today the Colt New Service was not a heavy weapon. Because of its low weight, it is an excellent belt gun, as it does not pull your pants off, even in 45 ACP or 45 LC. Both are excellent defensive cartridges, I prefer 45 LC as the heavier bullet is a comfort to me.
An updated Colt New Service would need a better grip frame, the original grip frame is not dimensioned for human hands. In my opinion, a thick front sight, half moon would be great. Original front sights are slightly thicker than a playing card. Combat shooting of the era was against round Bullseye targets and a thin blade would work well with a 6 O'C hold. The sight picture looks like a Popsicle. I think thin front sights are horrible in every other situation. The half moon sight would be snag free from a holster, and works great for a defensive weapon.
I do not like the delicacy of the original lock works, so I don't care how they are replaced, but I would want something more durable, and something that does not require factory training and years of experience to work on. Without
Jerry Kuhnhausen's books, specially
The Colt Double Action Revolvers: A Shop Manual, I would never have puzzled out the multiple surfaces of the Colt hand.The original mechanism is too complicated, gets out of time easily, and requires hand fitting, which only works well when there are plenty of trained gunsmiths around.
I do think the concept is great, a medium weight big bore revolver, fixed sights.