What about an "I" (or H if your font is sans-serif) shaped system? Like the Vast "stick" but with two sticks attached to the end. Seems like that would multiply the livable area by a much greater factor than it would multiply the number of launches. If I understand correctly the Vast is already a multi-launch system, so it seems like the obvious change.
If you can tolerate +/- 5% gravity level (which should be doable), instead of a stick for the habitable area you can rearrange the modules into a more compact blob, which should reduce radiation shielding. In LEO it doesn't really matter but it's more important in deep space.
