The best thing to do would be to set up auto import folders, and do auto-tagging based on the folders. See glynor's excellent guide here:
http://yabb.jriver.com/interact/index.php?topic=68462.0That way, YOU can decide what MC tags media subtype as. For example, if you make new home videos, just move them to the auto-watched folder that is set up to tag new entries as Home Video when they are imported.
Then, when MC sees that new stuff has been added to that watched folder, it will tag it as Home Video, as directed to do so by the auto-import rules.
Of course, you are free to create new library fields and populate them automatically based on any rules you can concoct. Just read the guide carefully, proceed slowly and ask for help as needed.