what is the UCCE (~ ICM) version? Is there OS hardening applied?
By the way, yes, if you mean the local "administrator" account, you can do whatever you want to do with it, provided you don't lock yourself out - this should not happen, naturally, having all ICM servers in the domain and you can always use the domain admin (or a user belonging to the domain admins group).
By the way, I don't really see the meaning of having a local administrator account being enabled. :-)
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.