I would like to add a base class to app/code/core/Mage/Payment for echeck processing. The idea here is that PayGate modules could then inherit from this base class to use/override basic echeck functionality.
If I want to contribute my work back, should I build this in Core or in app/code/local/MyCompany/Payment?
Would it be best to start by copying app/code/core/Mage/Payment to app/code/local/MyCompany/Payment and start making my changes there?
Thanks for all input