Did you find out a way to do it? Please let me know as I am also trying on the same thing
To accomplish this you you can include your ds.xml file in the application.xml descriptor. Of course when you are building your EAR file your ds.xml has to be placed in the EAR on the root level. If you place it on a different level, such as EAR/conf you need to specify this in your application.xml
I added the following:
Example for the root level
Example for the conf level
I am not sure if this is the right way to do it, or if application.xml is even supposed to be used for this purpose, but it works. I also included my jms.xml file in a similar manner.