I have MCA 2017 that i use in my smax, you need to replace only content of map folder (map folder are located on two place) on MCA SD card 2017 with new files from MFD 2018 SD card.
1. Ford MFD Western Europe 2018\cryptnav\data\data\map
2. Ford MFD Western Europe 2018\cryptnav\data\connect\map
Folders are at same location on MFD and MCA SD cards.
FORD MCA WEST V7\cryptnav\data\data\map
FORD MCA WEST V7\cryptnav\data\connect\map
The second part you need to use old SD MCA card i use from 2011 to downgrade navigation software on NX unit and than used modified MCA SD card 2017 with new map to update NX unit and it was successful. I have new updated map.