Sure: how about a large ship that consumes asteroids, and has production facilities and factories set up to mass-produce ships. It goes around swallowing asteroids and pumping out ships.
Since moving costs fuel, and sitting stationary does not, there's really no reason to have mobile structures considering the amount of mass you'd need to move - and thus need an extremely high amount of fuel to move. In other words, it would cost less to simply rebuild wherever you want to go. Imagine uprooting an entire city, and moving it to another location. It doesn't make much sense. Instead, build a new city.