This is a good request and we will implement this now (please give us one or two days to have this change released to all servers). Basically, we will add a new parameter called case_insensitive to all regex commands (e.g., regex_replace_all, etc.) just like this:
<n.regex_replace_all. pattern="abc" replacement="def" case_insensitive="true">
test test test test
I will let you know when this is released. Thanks for the feedback.