The ability to replace the JSF impl was released as tech preview in 6.1.

Validate that sufficient testing for the feature exists in community or create the testing.

Full support for the ability to change the provider. It is not a requirement to support any particular implementation (will create a separate requirement if that is required).

We need make sure that a subset of JSF implementations are known to work at some minimal level of functionality. (We won't be supporting replacement JSF implementations, we will only be supporting the ability to replace JSF implementations.)
There are two JSF code bases: Mojarra and MyFaces. One option is to select the latest version of each impl and spec version and run the TCK against each one. We can then say that this subset is "known to work" with EAP 6.3. The latest versions of each spec and impl as of today are as follows:
MyFaces 1.2.12 -> EAP 7 supports JSF 2.1+
-MyFaces 2.0.19
+MyFaces 2.1.Latest
+MyFaces 2.2.10

Mojarra 1.2_16 -> EAP 7 supports JSF 2.1+
-Mojarra 2.0.11
+Mojarra 2.1.Latest
+Mojarra 2.2.12
Integration points not covered by the TCK should also be tested.