In my opinion if imperfections concerns the unit cell as a closed
structure, and translational symmetry is partly brooken, it is visible
as a broadening of the diffraction lines.
If imperfections concerns the structure (interior) of the unit cell,
the differences in intensity arises.
The good example is FeAl alloy. It crystalize with cubic crystal
structure, but:
A2 - b.c.c. if disordered ( each location is occupied by 50%Al+50%Fe)
B2 - atom at 0 0 0 is Al, at 1/2 1/2 1/2 is Fe
DO3 - superstructure made by 8 unit cell of B2
L21 - the most ordered ( crystallographically), modified DO3.
But of course the disorder in unit cell structure can concern e.g.
location of the atom, occupation of position etc.
This topic is discussed in a brick by Cullity. He discuss
transition order-disorder in Cu-Zn alloys.
regards
Adam