I'm not sad to see the IP (aka PC) leave the GPR file. It's a concept that was past its freshness date in the 80s.
But SP's not a GPR? Wow... It makes a certain amount of sense, really, since stack pointers move in rather particular ways. Treating it specially may help when speculating memory accesses. I'm going to guess they have dedicated ways of generating SP-relative addresses for local variables, along with frame pointers.
Otherwise, it sounds very MIPS-y, at least superficially.