keep in mind that Epic (and presumably Scarlet) CURRENTLY CAN NOT PUSH OUT AN EDGE TO EDGE 1080 IMAGE. So if your client wants prores now, you will be delivering footage with black borders on some/all the edges of your footage. this makes any offboard recording as a new master dead in the water.
again, all current 5k resolutions are not 16x9 and the 4khd spits out 1080p but with a small black border around it.
this, of course is subject to change- one firmware update and this can go away. bring back 4k16x9 in addition to 4khd and I think problem will be solved.