FDE RAIM for tso145/6 receivers deals more gracefully with RAIM problems by deselecting the faulty satellite and, if you still have enough satellites, you can continue the approach.
Surely all RAIM kit does that? You need 4 SVs to get a 3-d position and 5 SVs to provide RAIM. More than 5 SVs gives you redundancy to maintain RAIM while deselecting SVs. If you start with 5 and then deselect one, you no longer have RAIM and will therefore have to discontinue the approach, no?