Dear augusto,
YES you can do that with JMS.
We have already customers that are using JMS to create websites for different countries or cities.
Sometimes they have several hundred of websites.
YES you can use K2.
It is also defined in the JMS tools definition.
See the list of extensions defined for the JMS tools and the one that can be shared.
www.jms2win.com/component/content/article/135
You can effectivelly create a JMS template that will define the rule to replicate websites that will give you to all your slave site information ready to use and that you will be able to change in each individual slave site.