I'm not a big fan of multiple choices once the user selected the desired one, so once the user "made his mind", I try to reduce friction as much as possible by "killing" any other non-needed choice.
In this particular case, what I would do is to use a multi step process: first, user selects the desired payment option. Then, user is directed to a page where he/she will see the process for that option and NOTHING ELSE. Thus, I can make a better use of space, there's no "noise" and no accidental touching of the other options. Keep in mind that this approach also requires an easier to manage process in case the payment process fails: simply add another window with a simple message:
Payment has failed #
retry / use another method
Now imagine what would happen if I do the whole process inside an accordion window, my method fails and then I have to use another accordion panel
So, IMHO, the "accordion approach" is not a good method for payment process because you have different screens, hence content is dynamic (causing the problems I mention above), while acordions are meant to be used with static content.
Here you have some info on when and whether to use accordions:
As you may see, while there's no mention of NOT to use it in payment processing, you'll notice it is mentioned as one of the situations to use them. Furthermore, there's not mention of using them with ANY dynamic content at all, only static
And finally, something that might be of direct interest for you: http://baymard.com/blog/accordion-and-tab-design (scroll to Better Alternatives)
If the content isn’t mutually exclusive, consider simply listing all
of the fields on the page or splitting them out across multiple form
steps. Our research shows that good checkout usability isn’t about the
number steps but rather how user-friendly those steps are. Whether you
have a 2 or 4 checkout steps doesn’t matter that much, what matters is
what users have to do at each step, and how they are asked to do it
(i.e. are users able to seamlessly progress through the steps).