Although CWA is not supported on the Front-End server it has been installed by others and is known to operate, but can be tricky to configure correctly. At minimum a second IP address needs to be configured for CWA to run on as the Web Conponents already use TCP 443 on the primary IP address.
But if you have OCS FE, OCS CWA, Exchange, and Sharpeoint all installed on the same host I can only images the level of headache that can cause. Ideally you should have 4 servers, one dedicated to each of those roles, with the AD Domain Controller separate as well, since that wasn't mentioned in your post.
Jeff Schertz, PointBridge | MVP | MCITP: Enterprise Messaging | MCTS: OCS