Custom provide fields using regular expressions

I saw it in vBulletin and really see a use in it. At the moment you can only define the maximum length of a field entry and what exact format it must be, but that is very limited. In my specific case I'd like to make sure that every entry has a maximum of 12 characters with the first being upper case and all the others lower case. No special characters shall be allowed. With regular expressions it would be much easier to prevent people from entering invalid information. I think it should't be very difficult to add an optional regex form field in the ACP custom profile field section that is just ignored if left empty. The syntax that is entered there is then directly used to check an entry entered by a user. So it's for advanced admins and fully optional.