Currently, there is not possible to create bond/team/bridge without any slave/port connection in it. nmcli allows to do it. There is no reason why this should not be possible in nm-connection-editor.
Bridge connections can be created without slaves in nm-connection-editor. The code allowing that also for bond and team is available in upstream branch jk/rh1075198-editor-team-bond (network-manager-applet repository)
I agree that bond/team should be able to be created without slaves and that bridge/bond/team should be consistent with each other. Patch looks good to me.
Upstream master commit: 8a5e838 editor: allow creating bond/team connections without slaves (rh #1075198)
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHBA-2015-0596.html