I would suggest that using a range rover and electric winch is too marginal for the job that you are trying to do.
Ist thing unless it is a very long cold winter forget about getting across bog with anything wheeled. You then have the problem of casualty vehicle being frozen into ground .
I would take a vehicle such as bedford RL recovery . about 12mpg ,45/50mph, with pto multi directional winch , also has spragging equipment to hold you still.
and has crane to lift sled on/off trailer . make sled(lightweight/flat moveable by hand(many ) so you can bury rear edge under front of vehicle to be recovered . winch sled, to casualty vehicle . use 2 pully sytem to force sled towards casualty and at same time winch vehicle up onto sled . When vehicle on sled, re rig to winch loaded sled out . You should then be able to winch uponto trailer secured at rear of RL . HTSH
I have done recovery for many years , in UK and Aus, upto CAT D9 and Antar , and the above is how I would do it