For a data point:
I mow an 11 acre runway (4800' x ~100') that has runway lights on about 3000 feet of the length. I use a 45 HP 2WD Kubota tractor & 7' finish mower, mowing in high 3rd gear. It takes about 2 & 3/4 hrs to mow, including using a zero turn mower to mow around the runway lights. Obviously, it's straight, level, and no obstacles except the lights.
I don't understand the need for a loader & 4WD, if all you're going to do is mow. Plenty of uses for both, but they don't involve mowing. In fact, the loader would be a big disadvantage while mowing, in my opinion.