Hmmm, this is a neat idea. But salaries tend to be sticky downward. What happens if your revenue drops back down to standard levels, such that the newly selected salary is no longer sustainable?
Perhaps a democratically selected bonus would be a safer option.
Is there any evidence this actually works? You're motivating your product by saying it helps you keep your job if you have a thick accent. Does your product work? How does it compare to competitors? Adding this information would improve credibility.
25% is really high and might as well be mandatory. Only a fool would count on not having to verify, especially when they don't tell you until the last second. This isn't a pilot program, this is a massive, invasive change.
Perhaps a democratically selected bonus would be a safer option.