Kip,
First of all, Welcome to the world of M-B!, and Welcome to this forum. You are asking your questions at the right place. You will find many truly knowledgeable people here.
I', with you on the engineering. My first thoughts when I originally encountered it- a vast two years ago, ( not an expert), was that " Someone thought their way thru this" and it seemed true regardless of what the current " this" I was workiing on.
The vacuum locking system is the " SU carburator" of the W123. They are a neat convienece when they work, butseldom work flawlessly as they age, yet never disable the vehicle. They are a tinkerer's dream as they just invite you to work on them. A very simple system, that holds the allure of perfection, but with enough old rubber aprts that leak, just a little. And the parts aren't expensive. As for disabling it---its up to you, but I like the central locking system. Get yourself a Mighty Vac--handheld vacuum pump and start finding the leaks. With persistance you can achieve perfection.
Anyway, enjoy the Benz.