Yes I have given serious thought to quitting CCR diving especially after Penny's, Zac's (in the USA not our Zac) and Rob's death's. All much better divers than me, all instructors and all faced with imposable situations on a ccr.
Digging into what happened helps a bit, because there is always a reason. However if they can screw up then I am twice as likely to.
I am 42 this year and I have decided to quit CCR diving and deep (past 50m) diving aged 45. I think CCR diving past 50m justifies the extra risk and complexity of equipment but less than that its not really necessary. I would go as far as to say 60m+ on CCR is safer than on OC. This is because you can run very high Helium percentages economically and you have almost limitless gas time to let you sort out a problem.
Having been at a humble 65m with an "issue" on OC i can tell you that gas pressure drops reeeeeeely fast when you don't want it to. However the problem on CCR is if you become stressed and start breathing harder you instantly think "whats wrong with the unit?" Just checking the PP02 is not enough to calm you down because you know there is Co2 and dodgy cells to worry about. I have had to have a little chat with my self down there and calm my self down but ultimately I have taken a leap of faith that its me not the unit and been correct / lucky so far.
IMHO if you want to stay alive on CCR you have to have more than adequate bail out with good high percentages of helium in it for deeper dives. You need to be scared a bit and you need to bail out if it doesn't feel right. Something I have failed to do twice now
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I think Full face masks have good safety advantages and gaged BOV's also offer a safety net for buddy diving and a far easier way of bailing out. However I think they need to be rigged to big off board tanks.
Apart from that you just have to accept that diving is dangerous.
ATB
Mark Chase