We have a Project Manager group and we give that group Manage access to the project on all templates. So any project manager can jump in and cover for or help out another project manager, since they already have manage access to any project created from a template. Additionally we have a dashboard for project managers with various reports that brings up that user's projects. Plus a "Covering" dashboard, which has all those same reports, but with a Project Owner prompt instead of the $$USER.ID filter, so whoever is covering can pull up each report for whoever they are covering for.