Hi James,
you are right and not alone in this point, there are several issues around migrating 'EJB-calls'.
the EJB is identified by it's name 'ejb:<app>/<module>/distinct-name>/<Bean>!<View>' and the selector will try one of the available references.
It is not possible to select a special server/bean with the current implementation.
With the management API you are able to create remote connections, but AFAIK you need to restart the server (which is also possible via CLI if you use doamain mode). But from my perspective this looks also not feasible :(
There are several changes in progress but they are still not finished.
I think there will be an enhancement that the application can have more control about the EJB-selection without such configuration and direct access to the JBoss specific API classes.
You might watch the following JIRA's EJBCLIENT-34 AS7-5047
Also I'm working on some quickstarts in this area, you might watch this documentation (keep in mind that the link might change for 7.2 and further releases).
If there are enhancements I hope that I (or someone else) add this to the existing or some new quickstarts to the "JBoss Developer Framework" in time.