JSF capabilities is not required by Seam Components content assist. CA for #{} in xhtmls should work anyway (after disabling/enabling Seam support).
I tried to reproduce the issue in Seam 2.2.0.GA:
1) seam generate-project
2) import the project to JBT 3.1
3) disable Seam support for the project
4) enable Seam support
5) open home.xhtml, try ctrl+space on #{}. It works properly.