do you think adding a property to $regsubex is a bad idea?
Although I have done this before, I have never really liked using a property to change the behaviour of an identifier because it precludes the use/addition of other properties. It would be better to find an alternative method. In this case, custom regex modifiers have been added in the past, S and F, for other uses. So a better option would probably be to add a custom regex modifier.
Update: I have decided to defer support of this to a future version. Changing the current routines to support both ANSI and Unicode PCRE calls at the same time requires far more changes than supporting just one or the other. So the next beta will revert to ANSI PCRE for now.