I'm a bit anxious about cutting the hydraulic hoses, so I did some mock-ups in CAD. I currently have 660mm wide bars and a 100mm stem, but I want to keep the option for wider bars with a shorter stem because I think that's more common in MTB-land nowadays?
So I modeled the front half of the frame, a stem, bars, and an approximation of the angle at which the hose leaves the lever and is attached to the frame.
Then I measured the length of the hose with the current setup:
Then with a short stem and wide bars:
And then with a long stem and wide bars (unlikely combo, but I was curious):
The conclusion is that it doesn't seem to matter that much, so I can cut the hoses with peace of mind.