The whole category set up needs a revamp. Modern multi-purpose vessels often don't sit exactly in any one category, and often could be legitimately be classified in several. There is no category for con-ro vessels, which is an industry recognised category. There is no category for the newer type of windfarm support vessels. Offshore vessels in general are often multi-purpose, and have modules installed or removed depending on which type of work they are doing. The distinction between crude and product tankers is less pronounced now, with many vessels able to carry both, and frequently do on consecutive voyages. Even ro-pax is a possible new category.
However to revamp this would be a mammoth undertaking, and to make it work would require 1000's of photographs to be reclassified. Unless someone, or several people, can be found to do this, I guess we're stuck with what we've got.