There is a little problem with this way you doing it, which is : what if we have a FFD(5, 5, 5) then you can skin wrap that to a Box, but as you know inside of the Box is empty so how the interior FFD Control Points gonna get wrapped to the Box , in this case they remain at the same place. So to Fix it you just need to have a Box which has interior Vertices, so I wrote this little script which create a box like that regarding to the size of the box segments you need just change it as your box setting.
——————————————
boxes = #()

for x = 0 to 1 do
(
for y = 0 to 1 do
(
for z = 0 to 1 do
(
b = box width:10 height:10 length:10
append boxes b
b.position = [x*10, y*10, z*10]
)
)
)

–print boxes

select boxes[1]
macros.run “Modifier Stack” “Convert_to_Mesh”

for i = 1 to boxes.count do
(
i += 1
if i < 9 do
(
attach boxes[1] boxes[i]
)
)
——————————————

Good luck,
Ehsan Kiani.