Hi,
you can use an expandable Braided Cable Sleeve ( see below ) around your tether ( avoid tape or cable tie that can get your tether snag).
At the ROV end you can form a loop that can be attached to a solid point on the ROV thus avoid stresses on the cable thimble.
I described the process in a short tutorial here
Of course, you can reduce the length of the superimposed section, and increase the other part at your convenience !
You can also use a thicker sheath by using coreless ropes like this one :
