You’re correct you can not change  the template  for an existing  site… You can use WinAppTechnologies’ (www.winapptechnology.com) echo product to move some of the settings around or Coras Works’ (www.corasworks.net) Data Publisher to move the data.

You’re very unlikely to get folks to support  you modifying the database  directly since it means product support really won’t support you any longer.