Great! Used the search function of this forum - DOH - and found this topic that solved my problem:
The answer is PrefixDeploymentSorter.
Wow, this is helpful, I was having similar issues. I think this is a real outtage in the spec that there aren't deployment primitives that allow this.
You can also use a depends element in jboss-web.xml to depend on the jmx object name of your ejb 3 deployment