Then you can no longer rotate, unless you make it rotate when you push some additional button. The 3DConnexion devices have 6 degrees of freedom without pushing any additional buttons. That being said I have a SpaceNavigator and I don’t use it, it’s just sitting in a drawer and I use my regular mouse and keyboard even in Blender.
Makes me wonder if it would make sense to have rotary encoders for precision work -- something that would work like in an Etch A Sketch. The pointer could be positionned with great accuracy and wouldn't move by accident.
It may not be too hard to make a prototype with an Arduino. Or maybe somebody already tried it?
1: https://3dconnexion.com/ua/product/spacemouse-wireless/
2: https://youtu.be/wGx4T8OH10Y?t=44