Your name matches your question well.
Is there a perfect system short of what we see being applied today and again?
No.
Is there a reasonable approach that could be taken rather than lumping everyone into one mass group of suspects until cleared?
We have had 5 years to come up with one.
"Is there a reasonable approach that could be taken rather than lumping everyone into one mass group of suspects until cleared? "
"Reasonable" depends on which side of the equation one is and is opinion not fact based.
Much has been made of the proverbial "80 yr old woman in a wheelchair" being frisked. Is it not "reasonable" to presume that as soon as they are given a free pass, TERRORIST would exploit it? Think.......we use civilians as human shields, we don't mind killing kids!