I have reservations about Velcro. It may be fine for a bike that runs around the town, but it you venture for any distance as I occasionally do, I would be worried about losing the plate. As debris builds up on Velcro surfaces, their ability to grip diminishes. They eventually wear also.
What was great about that plate frame was the it was spring loaded and pushed the plate up against the inside of the frame. I've been thinking of ways to modify a standard frame to do the same, or similar. One thing I was thinking a about was a hinged frame, either from the top/bottom or side, with either a detented cam lock or, simpler yet, nylon butterfly bolts.