Add multiple FQDNs for client access SharePoint 2010 with LTM

First things first, that HTTP/1.1 question relates to a simple monitoring configuration, and specifically what Host name the HTTP monitor sends to SharePoint in its request, because SharePoint cares about that sort of thing. The monitor only checks with a single host name and there's no facility to add or switch between host names in the iApp. You'd likely need an external monitor script to do such a thing, if you really need to.

As for a client request, the LTM VIP shouldn't get in the way of what the client sends, so assuming you have multiple host names that resolve to the same VIP, a SharePoint server that serves all of these applications, and a client makes a request for a specific host name, that same host name will arrive untouched at the SharePoint front end.