Thanks for comments, lads.
I think I'll have to retain in "long-and-skinny" form in able to have as light landers as possible. Those are supposed to refuel in the Moon surface; either from cargo landers or/and with ice founded...
Not really sure what heuhen meant, but here is a rough section sketch of the vessel.
I was thinking something along these one (lightweight, somewhat easy to transport):
(Inflateable station structure)
The lander would have to be transported from the surface (earth), on a separate transport system anyway, before getting connected to the "space-ship" itself up in space. If not the lander is transported in a sort of container, that is just adde on the spaceship.