It's either mechanically connected to ISS, which has some advantages and disadvantages, or is a separate module which closely follows ISS on the same orbit but

It's either mechanically connected to ISS, which has some advantages and disadvantages, or is a separate module which closely follows ISS on the same orbit but is not mechanically connected to ISS, which of course also has advantages and disadvantages. No, it's not going to be absolutely massive engineering effort... why do you think it will? https://space.stackexchange.com/questions/35960/how-many-times-would-two-astronauts-have-to-run-around-skylab-to-turn-it-by-10-a https://space.stackexchange.com/questions/35960/how-many-tim...