[curt.clifton]

Note that the link points through the Spotlight cache. Caches are intended to be temporary, so that seems risky. (I don't know how stable the Spotlight cache is in practice. It may be fine.)

It seems like this is a problem with MM not using the system URI handlers. OmniFocus installs a handler for 'omnifocus:...' links. Have you asked the MM folks about providing general support for links?