Drilling into the body of a camera that costs multiple thousand dollars to add a second screw seems like a risky maneuver and definitely warranty-voiding. I would personally advise against this.

Adding Velcro doesn't seem to me like it would do much for vibration or slippage (large rotation, yes, small scale rotation, not so much), since Velcro is not a rigid connection. Rubber or similar spacers can help but it's still not great. I use a plate that's got a lip on it to prevent twisting (which was a happy accident, because I actually ordered the wrong plate).

To me, the degree to which a camera is likely to see a built in Arca Swiss plate is inversely proportional to the degree to which it costs multiple thousands of dollars because the higher the price the more modular the design. The reason for more modular designs is that the variety of systems with which high end cameras are designed to integrate tends to be higher. Or conversely the more likely the camera is to be designed to lock the photographer into a proprietary systems sold by the camera manufacturer.

In terms of adding a second screw, a multiple thousand dollar camera body is probably not the ideal first subject for a person who has never disassembled a camera or done similarly fine grained work. Such a person should perhaps hire a technician or practice on broken equipment first in cases where such modifications seem worth the effort/cost. Hoping camera manufacturers would design around the edge case is not much of a plan.

I think the inverse proportionality is probably wrong since entry-level cameras generally never get mounted on anything. Arca Swiss mounting on my mom's camera wouldn't be particularly useful.

I don't think a multiple-thousand dollar camera body is a good target for invasive modifications unless it's already out of warranty, regardless of whether the change is being made by someone with the appropriate skills. I also doubt that the result of such a modification would be very good anyway. Without being part of the initial design (e.g. a captive nut embedded in the base), the best aftermarket modification would likely be based on either threads tapped directly into the body or a nut essentially glued in place.

I'm a pretty avid DIYer with a lot of tools, taps, dies, vises, etc.

I would not feel comfortable either 1) drilling into the bottom of my DSLR, or 2) taking it apart to see if I could safely drill into a given spot.

I would say there's quite a lot preventing me from modifying it, and even more to prevent normal users.

I mentioned cyanoacrylate for those reasons -- although other adhesives might be better, it seemed like a place to start. Anyway, one of the themes of my comment was that if it's a problem there are alternatives to hoping the camera manufacturers will address what is mostly an edge case that can be mitigated with attention to detail during the selection of accessories and their use in the field. I mean after a while, experience will lead to checking if the plate has become twisted before operating the shutter. It might take years for someone to recognize the problem and gain that habit and most people with cameras probably will never even experience it as a problem because it never is for them...because most people don't use a tripod most of the time.