This of course is the advantage of using the old "shared add-in" project types – you can build one add-in that targets all versions of all Office apps that support COM add-ins (ie, 2000 onwards). The question is, can you do something similar with VSTO...

First, the Office client apps are COM-based. Normal COM activation relies on the registry. COM registration is a "last one wins" model. That is, you can have multiple versions of a COM server, object, interface or type library on a machine at the same...