Great points. I had actually thought carefully about the safety aspect, and should have mentioned that earlier. In addition to many hours of riding, frequently inserting and removing my hand, I had to QR once while using the strap.
The wrist strap MUST be large enough to avoid lock-in and to be able to quickly remove your hand at any time. It's not hard, if you try..... famous last words?
All you have to do is open your hand, thus letting the strap (and bar) go.
Velcro - I considered it, did not have anything handy. Maybe next time. But opening the velcro as in the picture requires the other hand (not safe if you ask me; whereas to get out of my simple strap, just open your hand). The idea of a detachable wrist strap could however be implemented in other ways.
Death loop - yes sounds scary, never had one. Equipment failure can be prevented as well, at least to some degree (replace older parts, ride underpowered, mow the lawn, avoid difficult conditions etc).
Ergonomically, wrist straps are extremely good at dealing with relatively low forces for long periods of time. At the same time,
safety is of paramount concern, and your mileage may vary.
If opening your hand to let go seems unreliable to you, a very safe version is likely doable. Just one idea, use an attachment method - thin line, rubber, plastic - that is guaranteed to break above X pounds of force. Finally... you can have a wrist strap on your bar and use it sparingly, or not at all. User beware.