Printing Payroll Checks in Peoplesoft Payables 9.1/PT8.5 from external source without PS Payroll ins

We are implementing PS Payables 9.1 with PT 8.53 and our customer is currenlty using check writer software to print payroll checks from external sources. They would like to use PeopleSoft Payables instead. They do not have PS Payroll, the checks requests come as csv files with all the data to print them. They also have standard checks requests and for these we are loading data into PAY_CYCLE_DATA, then run voucher build to create standard vouchers and then run pay cycle to select and generate payments. Has anyone ever run into this situation? Our search retrieved nothing except lots of information to print