For custom fields, it should be an option to create a masking structure. For example, if I need to record an email address on a text field, I should be able to enforce that a proper email address structure is in place. For dollar amounts being recorded, I should be able to enforce that there is a decimal point followed by two digits.
Regex structures could be used to achieve this but I believe there are easier ways for the administrator to define this structure. Ideally this structure would also be enforced in the API layer, not just at the UI level.