It's not possible to Add JSF Capabilities to JSF project after they were removed.

Steps to reproduce:

1. Create new JSF Project

2. Open Web Project view and Remove JSF Capabilities from JSF Project using popup menu

3. Open Package Explorer and try to Add JSF Capabilities using popup menu JBoss Tools > Add JSF Capabilities. It's not possible because JBoss Tools submenu contains only one disabled menu item with label "Verify".