In your situation you don't need to lumber yourself with a Subaru.
As much as I loved mine, the parts are expensive, when you can get them, and even the non turbo ones are very thirsty due to the full time 4WD.
The clutch is also a very small diameter for the power outputs and 4WD, I changed mine every 40K miles.
I don't think any of them have a low ratio box either.
I had an imported Legacy GT (Twin turbo) for 5 years, it towed my old Flatacraft Force4 very well, but did about 15 mpg and got through tyres, brake pads, clutches etc at an alarming rate. Oh, and was a group 19 insurance
I'd suggest looking for an old Sierra 4x4 Estate, just because I like them better than the Mondeo, but don't know what insurance group they are now.
Audi also put 4WD in some of the old 80's and 100's with smaller engines I think.
Have you tried any angles on insuring the Disco as part of your company?
or putting any limitations on milage etc?