Have new users register in the comment box

Currently I have only guests posting on my blog and I'd like them to be able to register to the site inside the comments box, maybe just add a checkbox asking if they want to be registered. That way they don't have to go to a separate registration page, make it much easier to get new users. I don't want them to log in with their social media sites like Facebook etc. I want them just to check a box, which makes them registered user and they automatically puts them in MyMail email subscriptions. Maybe you could integrate with the MyMail plugin, ask them to help.