Yes looking forward to the range report and pictures. During freedom week in California I was able to get 17 round mags for my 659. They are flush fit Mac Gar Mags. They would work in the 59 also. Not bad for an all metal DA Handgun.
Is it viable? Yes, but with a few points that have been mentioned already.
I believe Illinois State Police has more experience with the 59 than anyone else. I would simply search using those terms for extensive information on what works and what doesn't.
Personally, for carry, duty or home defense a handgun HAS to have a rail light. Obviously, that excludes a 59. But for a range gun...nothing wrong with it.
We had issues with the second gen. Low round count guns were showing frame cracks. At first it was mainly the 669's with cracks in the rails. Then a few 659's were found with cracked frames. Smith is out of the repair business in the metal framed lines.