Abbreviated registration: just email

Hi
Is there a plugin or would it be "complicated" ( meaning it won't work on a v155 ) to simplify the registration process.
There are plugin to simplify the checkout, the COWR (? if I recall the name), a guess checkout by numix etc...

But I'm looking for a way for the customer to register only with a email, password , and the newsletter checkbox.
It's easy, and If a customer doesn't do a purchase , I don't need his/her information ( perhaps others do )

If a customer adds a products and goes to checkout , then yes, it would be redirected to the account details to provide all the other info. If not, maybe at least I can still maintain contact by the newsletter.

I've seen this files (more or less) , while I was changing the FAX number to be a VAT number and display it in the admin side, but that's all my understanding about if this is possible, and secure.

Thanks

ps: I'm not asking for the code , not even close, just some ideas if this as been done, and if it's achievable with the present structure of 155 and all that it's implied in the registration process.