The "built-in" support you are talking about where it leasts each gateway type by its real model number is used for MGCP signaling. So the AS5300 and AS5400 will probably be able to speak MGCP with CallManager at some point in the future, as far as backhauling ISDN signaling, etc. but when CallManager 3.1 ships I don't think this will be the case. Also the CCMAdmin will have to be updated so that it knows the slot and numbering layout in those chassis types.
In the meantime, use it as an H.323 gateway. That is the gateway to select if you want to use ANY H.323 gateway, regardless if it's a 1750/2600/3600/5300/7200/whatever if you just want to use H.323 signaling.
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.