As I understand it, the long term plan is to be be able to manage UCMs from GDMS. I can appreciate how complex this task is and how much work it will take to successfully get full UCM integration into the GDMS.
That being said, I believe a necessary first step into UCM = GDMS integration that is needed now is the ability to import/sync the extension configuration information (ext, auth ID, password, UCM IP/FQDN) from the UCM to GDMS.
I use UCMs as my VoIP server for my clients. Under the current setup I am going to have to manually transcribe or import this info in order to configure the GDMS managed phones at the start, and as I add/change/remove extensions on the UCM.
IMHO, this should be something given priority in the GDMS implementation road map.