You can do this if all traffic should first go to the main site and not directly between sites. So, if the main site WAN side (fiber side) is 10.1.0.254 then the default route on each of the other site’s routers would be this address. This means that all traffic between sites would go to the hub site and then back out to the destination site. This may or may not create performance issues but does bear watching.
In the IT trenches? So am I – read my IT-Trenches blog.