You can register MCU on VCS for VCS endpoints to use MCU as well, and depending on your route pattern configuration towards the SIP trunk on CUCM, 99XX phones can join up as well.
I don't particularly know your dial plan that well to offer advice, but if you have CUCM with SIP trunk to VCS and MCU either registered as H323 or SIP, 99XX phones or other devices should be able to hit the route pattern towards this trunk and join calls if required.
Best place to start though is go through the deployment guide for X6 and CUCM integration, and tweek rules etc once you get calls routing to and from VCS.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.