As a baal koreh always seeking to improve and perfect my reading, I long ago started using proper throated ayins and resh, then worked on dagesh hazak, and at present I am working on the proper beged kefes rafehl. Bet and Peh, which involve only lips and not teeth should reasonably not need teeth in the rafeh case. Rafeh gimmel as a gh and not as the teimani jh, and rafeh dalet as dz or dth. The aspiration of the dalet makes the halacha of Ehad in shema more mashma than those that erroneously pronounce that dalet with a shva nah. While you are at it, there are nineteen soft daleds in kriash shema, plus the kinui we use for Hashem’s name also is with daled rafeh. It would also stand to reason, thate there should be no redundancies, so sin, shin samech and kuf are all problematic. I have seen the inverse of the litvish lack of shin in some sfardi minhag as the lack of sin, and those that have a soft and hard very gutteral kuf.
