We tried to start using HTML as a base format for templates, but the outcome we got was fairly disappointing. It’s because all known HTML importers are rather primitive, and it is almost impossible to create document with more or less sophisticated formatting.
Nonetheless, if you don’t intend to use highly complex formatting, you may use HTML as a basis of templates. There is a special class named webodt.HTMLTemplate which behaviour is similar to the same of webodt.ODFTemplate. So you can start off with:
>>> import webodt
>>> template = webodt.HTMLTemplate('test.html')