I currently have a kioti DK45 4x4. You can put cat 2 or cat 1 arms on it. It is sort of a tweener tractor. In hind sight, I wish I had bought a name brand in the 70 hp range. At any rate, I keep the cat 2 arms on it all the time, but I use a mix of cat 1 and cat 2 implements. I just put bushings on the cat 1 pins of the cat 1 implements. You do need to be careful when using cat 1 implements on a larger tractor. For example, I have no issues with my FIMCO 55 gal sprayer that has cat 1 pins. However, I was using a cat 1, 4' bushhog on it one day. The tail wheel evidently hit a stump at an odd angle and did not spin and jump over it. In stead it hung. Other than a little bump, I didn't even know what happened until I happened to turn around. The tail wheel was missing and the tail assembly was bent. With a smaller tractor, the tractor wheels would have spun instead of tearing up the implement.
Having said that, if you are careful and pay attention, you can use cat 1 implements on cat 2 arms. Just think about the kind of equipment you are using and what over powering it might do and pay attention. I would not use cat 1 ground engaging equipment like a disc on a larger cat 2 tractor.
I do find there is a much larger market for older cat 2 equipment than for the smaller cat 1 stuff.
Thanks,
Jack