I would like to see them introduce an "umpire's call" equivalent, where the call stands but the challenge is retained. The NFL does this a little, in that they draw the distinction between "the call is confirmed" and "the call stands," although since in that league you lose your challenge regardless of success it doesn't mean much.
Even if they don't introduce allowing the challenge to be retained on an unclear call, though, at the very least introducing that language makes it clear when they're saying "we just can't see it clearly enough to be 100% sure and overturn," which would quiet down a lot of complaints I think.