Checkout Field Editor for WooCommerce

Hi,
I recently bought Checkout Field Editor, and it’s doing what I need. But one this that would be a nice addition is more options for restricting/validating a form fields input.
I’m having a form where a required field is a text field for entering a HostID/MAC address for a server. That field should only take 12 characters in hexadecimal, nothing else. So it would be great with a feature to add those restrictions, i.e. only allow characters “a-f” and “0-9”.
I’m sure there are loads of similar, but different, other situations like this where this feature would be great to have.

Cheers,
David