1st stage reusability matters more so they can reach a cost model similar to F9, second stage is really just bonus.
If they never get the second stage working with reusability they could strip the design down to a simple S2
If they never get the second stage working with reusability they could strip the design down to a simple S2
Second stage reentry is necessary for this thing to ever carry people, ostensibly the mission the ship was designed for. It is a hard requirement.