I think Iceland deserves the R, the A9 wouldn't be useful there, as I am guessing its mostly landscape stuff you are doing.
Definitely, I usually take the D850 + another Body and that's been awesome so the R will definitely be taking a trip (assuming I like using it). The A9 would be for a second body as I also like wildlife, motorsports etc.
At this moment I'm juggling 3 systems, various bodies and would prefer to get down to 2 systems (I'm keeping the Fuji gear as they are just great little cameras).