2.5 cm is way larger than 2HP, the smallest width you see in Eurorack. And pretty much the point of Kosmo is to be larger than Eurorack, with larger knobs and jacks and more space between controls. But for instance I have a dual ring modulator in Eurorack, there are no knobs or switches, just six jacks. It’s 4HP wide and has no need to be wider. A similar module in Kosmo has no need to be more than 25 mm wide.
Of course I say this as one whose first and only Kosmo module is 25 mm (with one knob)…