...if you compare the size of the Surak-Class with the Deadalus-Class you'll see that there is not enough space in the Deadalus-Class to carry this "new" drive system!
Who says you need a new drive system?
It's not the drive, but the size of the coils.
In the mirror universe episodes, Trip was looking at a
schematic of the U.S.S. Defiant and made a comment
about the size of the nacelles' warp coils. He was so
impressed by the size of them, he estimated they could
generate warp 7 speeds.