Yeah that's all good to do every now and then, but having owned Triton, Rodeo, D40 navara, D22 Navara - I wouldn't want to be towing a heavy work trailer day-in, day out, every day with them, they will just fall to bits. Hills starts, reversing trailers onto slopy/muddy work sites, driving in peak hour traffic, etc etc. It's not just the engine that has to deal with the weight and regenerated stresses of towing a heavy trailer, it's just about every moving part on the vehicle that is affected, and I just don't think the smaller trucks are built for it.
Don't get me wrong they are brilliant for what they're designed for, but if you're doing heavy work I think you need a heavy truck, if you want to take it easy and look after your vehicle.
I guess if it is just a single axle builder's trailer that will be no probs at all, but if you're talking a big dual axle job with machinery & concretor/brickies gear then that might be pushing it.