although I am only 45, I have been wearing bi-focals for over 35 years, until about 10 years ago, they were plain glass for distance, and a reading prescription in the bi-focal part.
It's one of the few things that the Army doctors did right when I was a kid. The theory was that I wouldn't have to take 'em on and off as much, therefore less chance of damaging (or losing) the glasses.
Back then, there was no such thing as the "no line" bi-focal. I got used to wearing them with the line, and I don't even see it anymore. It's also a lot easier for me to 'transition' from distance to reading prescriptions.
My advice to the OP, would be to look into some 'regular' with a line bi-focals in his normal Rx and go from there. I don't have any issues with using open sights or with some sort of optics. I just focus on lining up the front sight with the rear sight, and I expect to have a slightly out of focus target.
Exco