How about something like an "Orb of Choice." One of the orbs that gives you visions (faith version) of how things would have turned out had you done something differently, or, rather (science version) delves on a surface level, allowing you to look, at alternate quantum realities. Would be an interesting story exploration tool for a crew to accidentally get explosed to the light of the orb, and not realize they're in the equivalent of a mental holodeck, living their lives as if they'd done the opposite of their major regretted decision, wondering if they could possibly fix it, only to have it vanish with a flash...
I'd always wondered what would have happened if Picard had preferred the live he'd seen in "Tapestry."
The Doc
So you think, 'Might as well,
Dance a Tango to Hell,
at least I'll have Tangoed at all.'
-- "Rent," Jonathan Larson