Sure, though you could do something similar to the Conditional options and have a checkbox to turn on validation rules while usually hiding the interface. I might even have a "Use regular expressions (click here for more information)" checkbox under the rules input box so that if unchecked you simply use strpos() or something similar to find a string occurrence.
Implementation using hooks adds a ton of complexity to the customization process, especially when you have users creating new forms on an almost daily basis and don't want to have to apply the same validation rules to each form. In terms of implementation, it would almost be easier to just use jQuery instead.
Slightly off-topic, though related - do you accept code submissions?
Posted 9 years ago on Tuesday August 3, 2010 | Permalink