well to go with your theme, get rid of the msd box.

go with a points distrubter with a petronix setup instead.

not as much control, but less to fail.

however, I must disagree with your assessment on efi setups.

today there is a much wider range of efi setups than ever before.
there is a post from the fast efi guy detailing all possible failure modes and what is likely or not likely to die.

I have converted mine to efi and been running it for 3 years now, others probably longer on more primitive systems.

the only thing that had died on me is the fuel pump, and that was due to poor mounting location.
since mine is one you have to tune, yes I find myself tweaking things still, but with the 3 or 4 self tuning systems out there, you don't even have to play that game anymore.

now it isn't 10 or 15 years old yet like the mustang you are talking about. But lets get real.
15 year old cars don't run like a dream. somethings need to be replaced periodically.

don't know what actual issue you saw, but take a step back and remember what you had to do to your old car to keep it on the road.
what spare parts did you have in it so you could get it running and drive away?

diagnosing a non running condition is the same today as it was 40 years ago.
spark, air and fuel are still needed.
how they get there is a little different, but people forget it is still the same things to look for.