A/P Processing - Produce Bank File

I need to create a new write program with a new pay instrument using P04572T1 or P04572T2 (automatic payment) as the base. I want to use a different document type for these transactions instead of 'PK' and 'PT'. How much effort is there to create a  new matching document type for these transactions? Which programs has the document types hard coded? If i used a different document type, will it cause any problems with voids?

It was a lot research involved. The solution that was implemented for this was to clone P04572T1.  The steps are listed below on  how this was set up.