Apache ODE is a BPEL implementation which built on Axis2. Actually what they have done is , has written a application which extends AxisServlet and do some additional processing. Meaning they have written a mechanism to create AxisService from a directory which contains BPEL configuration files and WSDL files. The created service has a common BPEL message receiver , and which handles the application logic processing. In simple word thats what ODE does (I agree the process is more complex and more complicated).
However with this approach I see a limitation (may be thats what ODE wants to support), that is you can only use this as a way to deploy BPEL and access them not other kind of services. Because Axis2 architecture is more powerful than this , we can do much more useful stuff with Axis2 than this. So it might be very useful if we can add the BPEL support as a deployment extension to Axis2. Since Axis2 has custom deployer support which we can use to deploy BPEL.
Not only that we can start the BPEL server inside the Deployer and handle the deployment logic inside our deployer. Once we do so we can register that with Axis2 , as a custom deployer and provide a way to deploy BPEL services as an archive file with much more flexibility. Not just tell how and what we can do with ODE and Axis2, I actually has implemented the logic and have the working code in my machine. Probably those code would be integrated to WSO2 WSAS. Then you can get the power and benefit of ODE and deploy BPEL services in WSAS.