Ah, that looks a little complicated and it might be better to just spin off new threads. @Jon_Shier, do you think you have enough of an idea on what to do for Character properties to start a pitch on evolution? Alternatively, I could start a more open-ended preliminary discussion with some guidance.
More details of String's ABI settle by the day, so it might make sense to continue that avenue of discussion in a new thread anyways. This is likely a prerequisite for the performance additions like a theoretical UnmanagedString and exposed performance flags anyways.
@anandabits has already started a discussion about the generalization of pattern matching at Generalized pattern matching - #2 by AlexanderM. It might make sense to pile on there for that.
For regular expressions, there's still a lot of syntactic holes in the straw-man. A new thread with a new straw-man to be knocked down is in order. As immediate focus is on ABI, it would be a slow-moving thread, but I think it would make sense to start in a week or two.
I do want to begin the discussion (perhaps on "development" at first) about the String interpolation performance issues. @beccadax, are you interested in starting that? Do you want any help or preliminary discussion prior?
In a few weeks, I'd like to solicit thoughts on a "String Dojo" in the Using Swift category.