In a roundabout way, yes.
One of things I check carefully when I'm importing GEDCOMs is the Place List. I make all of the new GEDCOM place names exactly match places already in my database, which prevents unwanted duplication of both place names and fact/events for merged individuals.
Similarly, I go through the List Fact Types, and look for Fact Types to rename to exactly match my current list. I check both the fact name and the abbreviation, but don't bother with the sentences (since RM will use my existing sentences). So, in your example, I wi;; change a custom fact like Occupation2 into Occupation, and the RM import will then use my existing Occupation fact & sentence for those newly-imported instances.
To do this to a single database, takes a couple steps. First go to Lists > Fact Types and change all the custom Occupation2, Occupation3, Resince4, (or whatever) to make the standard "unnumbered" Fact Types.
Then, drag-n-drop the entire database into a new, blank file, and PRESTO, all of fact types will be consolidated.