What could go wrong if I select the 5.1 Runtime in the wizard and point to the 6.0.0.M1 installation?
If there's nothing in the Tools 3.1 version for the AS 6 version, in what version is JBoss 6 with all its features supported (e.g. CDI)?
Nightly build should have an AS 6 adapter but it is technically the same as the AS 5.1 adapter since there aren't really any vital differences between AS 6 M1 and the last AS 5.1 release (yet).
So there is no danger in using AS 5.1 with AS 6.
About CDI then last night build actually includes the first tooling for it - I need to blog it