Has anyone figured out to add this kind of functionality to the DBField class and subclasses without hacking the core? I tried Object::useCustomClass() but apparently you can only use that for certain core classes. I've been wanting to add a toCamelCase and toSnakeCase method to Varchar and similar classes, but I haven't found out how to do it without hacking core files.
webbower - as I felt it bad form to update the core in order to add this functionality, I asked on the General Questions forum on the best way to get this functionality into the core for a future release.
ImacSS - functions in the core esp round strings, date etc are just added when we need them in a project. I doubt there is a 'design' decision behind not including it so I'm sure if you submit a patch it will be included in the next release :)
As for your post "How to make a recommendation?" I didnt see it in that forum but anyway as a note you should usually make a ticket on open.silverstripe.com with the patch / changes you wish. If its a large change or an API change then post it to the ss-dev mailing list as this will generate some discussion