Yes, ZF had 6 ranges and two forward, one reverse gear since the late 70s. In the 90s they put a 4 stage powershift and a powershuttle in front of it, at the same time JD introduced the PowerQuad gearbox following that principle, and Case the Maxxum.
Current ZF gearboxes have 6 instead of four powershift ranges, and a wider spread between gears. Top gear gives 72kmh but is limited to 60kmh at 1850 rpm.
To really be a winner, you need to be able to take off with all four wheels spinning on the pavement in 2nd range, either to take off with a heavy trailer on a hill, or take off after a standstill in the plough furrow without lifting the plough. Then you need 2 gears overlapping with the 3rd range to make up for lost momentum during range change. Between 1st and 2nd you need just one gear overlap because you will come to a standstill changeing gear ranges anyways, and between 3 and 4 the momentum of the tractor is so big that it wont drop more than a single gearspeed during shifting from 3rd to 4th.
With too big powershift steps the engine doesnt run at peak efficiency, but with too small steps, taking off in a low gear just takes too many shifts, the shifting slows you down. The latter is the reason i have started to doubt dual clutch gearboxes in tractors, because tractors need finer ratio spacing than a Volkswagen, and both Deeres DirectDrive and VW DSG are not exactly faultless in real life. Therefor i think 0.85 ratio spacing and 7 powershift speeds, on a Lepelletier style epicyclic gearbox like ZF uses in automatic gearboxes for premium automobiles, is the optimum between engine speed, gear shift speed and comfort, and the ability to shift two speeds at a time when approaching a steep hill or sudden load increase.