I was told that some beaver tail 7.5t plant trucks were so well designed that they could manage 4t as a load. Granted the whole o license thing seems to make jumping up from a 2.6t mini unviable for the owner op. I did come up with the idea of several owner ops forming a sort of co -operative, buying into & sharing the costs of the movement vehicle, would this be said to be 'haulage' if only moving equipment owned by the co operative members?
Big hook stuff is more versatile than a dedicated beaver tail, but there is a big weight penalty because of the 'Multi Lift' equipment's weight, a local firm runs a 7.5t big hook but this can only move a 2t max digger. He uses a skip rather than a plant flat body in this size, so maybe weight to be shed here.
He also ran a 3 axle HGV multi lift but this could only carry 8t, - he used to offer machinery haulage but this seems to have been dropped along with the vehicle