Not totally sure what you are looking for. Your page structure looks just fine for me. If I follow you correctly you choose categories from project page, and then you want to show those projects in different domains?
Something like this should work:
- Create a new template called "view_project"
- Add page called "project" under each your sites and give those pages a template "view_project"
- Allow urlSegments for your view_project template
And code that goes into your view_project template should be something like this (written in browser):
<?php
if ($input->urlSegment1) {
$projectName = $sanitizer->pageName($input->urlSegment1);
$project = $pages->get("parent=/projects/, name=$projectName");
echo "<h1>$project->title</h1>";
// Or just echo $project->render();
} else {
echo "No project found";
}
And when linking to your projects you should use urls like these: www.site1.com/project/projectname/