You're thinking of a riving knife.
I, too, wanted a riving knife. A search of the aftermarket revealed no such thing available for a PM66. I looked into building one of my own, but I couldn't figure out any way to make one rigid enough to be effective, that would fit in the space available within the saw. The arbor bearings are pressed into a rough casting with no flat mounting surface anywhere near the blade. Also, the back of the blade comes very close to the rear trunnion as it retracts, leaving very little room for any sort of riving knife. The design I came up with would have interfered with the table insert for beveled cuts, so I gave up at that point.
In practice, the removable splitter works the same as long as you aren't making a blind cut. I don't know about other saws, but on a PM66, because of the design of the blade height mechanism, the back edge of the blade is close to the splitter throughout most of it's adjustment above the table surface, so the splitter comes into play right after the start of the cut. For blind cuts, at least for the ones I do, they are either very shallow, and the risk of the wood binding on the blade is small, or they are made with a dado blade, in which case a riving knife would be ineffective. Again, to me, what makes it effective is the ease with which it can be removed and replaced. This means I will use it every time, rather than hanging it on the wall or something.
FWIW, the Excalibur comes with anti-kickback pawls that are very effective. I also use a pair of board buddies and an assortment of push sticks to minimize the possibility of kickback and the consequences thereof.
Regards, John.