Re adding stronger magnets, some of those little super strong magnets might be dangerous around a smart phone or credit cards. We've had some of these magnets in the house and they are very hard to remove from each other, my concerns may be incorrect but I would want to find out from reliable sources about any risks around stuff that will be in your bag.
I have the older snap version, and when I saw the magnet version, while it allows one handed opening for easy access to a camera, a downside to the snaps in my experience, I was immediately concerned about the top opening easily when carrying on your shoulder if it caught on something, spilling your camera out possibly. I spent years carrying camera bags and am perhaps more aware of worrying about this sort of thing.
I still think zippers are the most handy for one hand opening to grab a camera on the fly, and still avoiding accidental openings when carrying.
Always comes down to compromises with bar bags, yet I still appreciate the light weight and no brainer waterproofness of ortliebs.