It was none other than Bjorn Landstrom in his classic "The Ship" that may have opened up another possible explanation for the Bruegel "galleons". This is found on page 118, illustration 297. It is actually a thought I had myself; it has to do with the shape of the bow, as well as the flags the ships are carrying.
These might be the ultimate incarnation of the caravel, and sadly an end in themselves.
I've speculated several times that the Spanish and Portuguese sought to combine the best qualities of the larger naos with the lighter, shallower caravels, and that this may have led in turn to the Iberian galleons. By the time of Bruegel's engraving, the ship that could be defined as the predecessor to their galleons, though, was already afloat.
The caravel was still in use, in various guises. A comparison of the Bruegel vessels to the larger Portuguese carabela redondas is interesting in what it reveals. In many aspects, they are clearly similar, save for the rig and the long, multi-decked sterncastles of the Bruegel ships. In essence, these could be the ultimate form of the Spanish caravela redonda. As to why the ships were built in the first place is open to speculation.
Clearly, they were heavily built for their class, whichever class that was.
My interpretation attempts to clean up the original somewhat, and I readily admit that some of the rigging is sketchy. However, this may be a fairly good guess as to what these vessels may have looked like. So many other questions remain, as no other illustrations can be found of them. They can be best thought of as an experiment.
They are singularly unique.