Right now the extensions are always part of a project. This means that loading more generic extensions such as a find and replace function would have to be loaded in each and every project you want to use it in.
Instead of being project based I am proposing to have extensions loaded on your computer. These extensions would either be loaded for a specific version or perhaps even from a generic folder and managed by some sort of extension manager from which you may turn them on or off for specific versions.
From the project you would then have references to required extensions which can then show up as a warning message if you do not have the right version of an extension already installed on your computer.