I am not sure what the consequences are for possible implementations, but preferrably, I would want to be able to use regexps in (find or (keep, or (findsubseq just as easily as I would now use strings or functions
(keep odd (list 1 2 3 4))
(keep (reg /nan/) (list "banana" "bonobo" "bandanga"))
(findsubseq (reg /\d+:\d+/) "The current time is 10:00 am")
When looking at http://arcfn.com/doc/string.html , there is an aweful lot of restrictions on when we can use variables, or functions as arguments, so maybe a lot of the string operations in there become obsolete if there is a regexp engine in arc.