The AMS can be located a small distance from the printer (Bambu recommends no more than a 3.5m bowden extension), and the distance is not a problem for my temporary setup (it will be about 1m of bowden tube between the AMS and hub). However the AMS bowden tube itself is a unique design, and an ordinary tube will not work. The Bambu AMS bowden tube has an inside diameter of 2.5mm (and a normal 4mm outside diameter), while most bowden tubes are around 2mm for the inside diameter (or less). A normal Bowden tube will cause too much friction, and the filament may not make it past the transition into a narrower tube as it leaves the AMS.
Of course there is a solution, which is $9.99 plus $7 shipping... It's more annoying that I could not think of any other spares to pick up while I was paying shipping anyway, but I need the tube to get the AMS back up.
Update: The Bambu Bowden tube worked perfectly, and the AMS now sits atop the enclosure (for now).