is it possible or we should build a module for that?

As I understand, there is no rules integration for the payment method.

I think that is an essential feature, as different charges, emails should be sent on different payment methods. E.g. if someone selects bank transfer as payment method, the order should go in pending state (not complete) and send bank payment details to the email.

Is there a schedule for such integration with rules?

Could you give me a hint on where to look to add this kind of functionality?

Should I alter the payment selection form, the payment module or something else?