Hi Julia
Yes, we've done this, following the instructions here for sub-templates:
xot.xerte.org.uk/play.php?template_id=81#v3.8section3
We have a basic XOT template (with the properties turned off and only a select number of pages visible) and a 'themed' bootstrap template (with Uni logo and some basic settings included).
The other way we use templates is by one person creating the project (template) and then 'giving' the project to others as their own base template.
Cheers
Yvonne