Captcha by Form Class

It would be great if I could assign captcha to forms by form class. Currently it looks as though I can only select forms by form ID.

I am using the reply module to generate forms on each user's profile page.

I want to add captcha to these forms. Currently if I do this by enabling the captcha administration links on forms, this only adds captcha on a profile by profile (page by page) basis as each form as a unique ID.

I can assign the same class to every form, and if captcha could automatically go on every form with the same class that would be awesome.