I agree about datasources. However, the integration goes deep here, as Designer uses configured DTP's Connection Profile to create a data source or connection factory. As Teiid Designer uses the connection from DTP connection profile to import metadata and as well create DS in JBoss AS for use with preview. I believe this is done as extension to DTP.
Teiid Designer does not really need any UI to manage any of these that I know of, as long as it has access to underlying API to perform these tasks then it works. Deployment, data-sources are parts that are generic in nature, there are few other operations on teiid subsystem that Designer needs access to, to full fill its functionality (ex:merge-vdbs)
One part I have seen JBoss AS falls little short is in describing properties for the connection factories (JCA connectors, the RAR ra.xml properties not exposed through DMR), I added JIRA asking for these but meanwhile Teiid fills this gap with its own operations on its subsystem.
max, bmlafond, it is your discretion to see what can moved to core etc. I will participate in discussion anyway you guys want.
+1 for hangout
Marking it for Beta, to be something to look at since it believe Teiid aren't actually using the various server notions/apis.