I have cut the steerer tube on my bikes few times without ever disconnecting hoses. In your situation it gonna be a bit more complicated since your not going to be able to slide the handle bar off that steerer tube. You will need to cut the steerer twice, first to get it low enough to pull the handlebars off still attached to the hoses, then a second time measured to final length.
Turns out it was fairly easy to get the handlebar off, after all. Cutting the steerer was a breeze as well - I just clamped down the fork on my workbench and free-hand sawed it off with a metal saw (helps to have some practice with sawing in general from all the woodworking I do). A bit of sanding off the burrs and it was good to go back on the bike.
Second time routing the four cable hoses through the handlebar was much easier, too.
Installing the headset
properly was a learning experience, luckily there's so many great videos available.
I'm moving on to install the STI shifter/brakes now and then setting up brakes, FD and RD.
Oh, and I forgot to mention, bottom bracket and crank installation was very easy. The crank spins super smoothly - I went with a BB that Lightcarbon provided (i thought i can't go too wrong for 15USD). Will have to see how it holds up over time of course, but I can easily switch to another BB if required, T47 be thanked.