Process Model - Design Approach

Could you please advise regarding the issue below:
There are several departments, each one having their own webMethods Integration servers. A BPM needs to be developed to orchestrate a business process, say, order fulfilment. Orchestration involves the functionalities across departments. Ideally, we can define these IS as different logical servers and associate the process step with the server. However, I’m wondering, can this be achieved by issuing SOAP calls. What I mean by issuing SOAP calls is: The entire BPM code can be created on one Logical server(design server). On the same server, we can create web connector services for each service that exists on other servers. Each process step can invoke the web service connector or a wrapper service(over web service connector). I think this approach is simple enough and easy to deploy. However, I couldn’t think of any other issues that might crop up when this approach is taken.

Please help.

Best Regards
Sivaraj Lenin