Here we part company (likely only a little). At the depth that I'm no longer completely comfortable performing an ESE, while my primary focus remains on my buddy, my secondary focus shifts to self contained bailout methodologies which means a shift in gear selection and emergency plans.
I'm not sure I understand where you're going with this Thal. I don't suggest that every new diver I certify is required to equip themselves with redundant systems before venturing past 50'. You either instill the value of the buddy system or you don't. The focus has to be on one or the other. As this is in the Basic SCUBA Discussion area, I'm not sure how helpful a discussion on redundant systems are?