Hi all ..
I was thinking that the only difference between the 2 devices is the partitions setup .. so, if there were a script to adjust the partitions before flashing the other ROM it should work ..
Or even a script to make the device has both needed list of partitions available ( with the loss of a few extra space )

Steps for Mi A1 should be :
Unlock bootloader
Flash custom recovery
Run Repartitioning from A1 to 5X
Push 5X recovery and Bootloader
Flash 5x Official ROM
Done.
Note: I have done something similar to HTC Desire about 4 years ago and it worked fine
I was thinking that the only difference between the 2 devices is the partitions setup .. so, if there were a script to adjust the partitions before flashing the other ROM it should work ..
Or even a script to make the device has both needed list of partitions available ( with the loss of a few extra space )
Steps for Mi A1 should be :
Unlock bootloader
Flash custom recovery
Run Repartitioning from A1 to 5X
Push 5X recovery and Bootloader
Flash 5x Official ROM
Done.
Note: I have done something similar to HTC Desire about 4 years ago and it worked fine