Riley was only on one or two episodes Lt DeSalle was much more integral to the crew before Chekov came along.. so much so even with Chekov as an established character some of the fanfics that attempted to complete the 5-year mission included Mr DeSalle's character in their production efforts.

There's a very simple answer to why Gary Mitchell in his uplifted state put the stone saying James R Kirk. Of course they were friends for a long time but Kirk in many instances said "Risk is my middle name." Since that was repeatedly said it explained why the error on the stone