HI,
If you didn't find it yet, we have a developer documentation which explains how to creating payment plugins for HikaShop and other things:
www.hikashop.com/support/support/documen...r-documentation.html
If you're in the USA, Authorize.net also offers that capability (storing CC and recurring). But again, that will require a development since the only recurring payment integration we did is for "PayPal recurring" at the moment.
Your suggestion is interesting. That could be great as another extension which would plug itself to HikaShop in order to add that capability, like we did for HikaSerial or HikaMarket.