Yes, we know of the support for -ds.xml files, this was added to JBoss AS 7.x after the many community members complained about similar support from JBoss 5, 6 days. The disconnect is, in JBoss AS 5 & 6, user could configure both JDBC data sources and JCA sources using a -ds.xml file. However, in JBoss AS 7, the JDBC data source subsystem is different from that of the resource adapter. I do not think I saw similar support for -ra.xml for resource adapters. It could be done, but it needs AS level code changes for it. You can certainly open up dialog with WildFly team and log a feature request.
These individual -ds.xml files files work best in standalone environment, so currently I recommend using the CLI scripting or Admin API for adding a data source for Teiid.