This is not clear and you mentioned that you would like to do something like a demo that you see somewhere.
Would you please give us the link because we don't see what you mean.
If you want to create a website from the front-end with a specific "templates" directory, you can get inspired from the tutorial video 13 in which you can also decide to have a specific template directory like in tutorial video CP 05 or event use a zip containing a specific "templates" directory prepared for your demo websites.
www.jms2win.com/tutorial#jms12x-13
www.jms2win.com/tutorial#jms12x-CP-05