Generic Java based Service wrapper with provision of pluggable products in back-end

I am looking ahead to re-design and build a new Java Based Service Wrapper (as Generic as possible) with, 1) 1 Web-Service with some desired operations 2) 1 EJB Message Driven Bean for Asynchronous data processing

The application is to be used as a document generation service ( afp , pdf and tiff), which is to be invoked from several other Java / non-Java applications.

Currently the application uses the below 2 standalone (non-Java) products in the back-end, for some actual data conversions.

1) ISIS Papyrus 2) Oxseed AFP2WEB

However, we are evaluating some other products to replace Oxseed AFP2WEB, for AFP to PDF and AFP to TIFF conversion in order to cope up with some other business needs.

Hence the idea is, with a generic java based service framework, we can plug-in and test multiple products in back-end and test / finalize one.

Any approach / idea on the same is highly appreciated.

Thanks a lot in advance.