An array of steerable ion engines hanging below the station (ie on the edge not in the center) can provide both reboots / stationkeeping and precess the axis, e

An array of steerable ion engines hanging below the station (ie on the edge not in the center) can provide both reboots / stationkeeping and precess the axis, eg once per year to track the Sun. Because trig, by "mixing" both maneuvers together it uses less propellant vs doing the two maneuvers separately.