I'm not sure who sets this 'industry standard', but I don't see why 30 minutes would be more appropriate than the current time (10 minutes). If anything it would just encourage abuse because the perceived advantage would be far greater.
I don't see how this affected you in riding Soarin, if you'd wanted to ride wouldn't you have just hung around nearby for the maximum of the 20 minutes it would have been before you entered the line?
The issues you describe are the people likely to get DAS though. DAS isn't FP+, you don't schedule a DAC 60 days in advance, you turn up an reserve a return time on the rides you choose - as and when you choose them. It's also very flexible in that there is no limit to its availability/usage.
Your back condition sounds awful, I'm glad I don't suffer that - however if the pain is that bad "fetal position, trying not to vomit or cry", then I can't imagine wanting to be in a theme park, period no matter having a GAC, DAS or FP+ in hand.