There *should* be no problems with this, as long as the devices you want to add are SCCP capable or IETF RFC 3261-compliant devices (SIP).
Of course, you will want to check to see if the device you want to install has been previously tested for compatibility. For SIP devices, please make sure to check if the phone has been tested and certified to work with CCM:
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.