are thereany players that employ a system like thisfor melody playing,ring covers 1,middle covers two ,index covers three and possibly four,or index 3,thumb covers 4 and 5.
the disadvantage being double thumbing is not possible when playing melody on 4,but this could be overcome by playing 4 with index.
so is the idea in bluegrass that a melody note is always followed by another note generally but not necessarily on a different string,to create a flowing sound.
the ring is obviously a weaker finger[but surely it can be strengthened],but this sytem I find much easier because its what i use on guitar for finger picking.