An alternative storyline to the Mars transport architecture: Tankers refuel starship, last Tanker gets mounted on the Starship for the Mars orbital injection burn, once on a Martian trajectory tanker repositions/tethers engines facing each other and achieving, for the populated areas(35-50m radius) 0.35-0.5g's with 3 rot/min. Could use front fin boosters for rotation/emergency stops during solar events when the Tanker could be positioned as a supplementary radiation shield. So... How long is the mars orbital injection burn and could that time be adjusted so the forces involved don't add to much structural weight if the ships are attached during burn?
Check out my design here:
It couldn't be done with a Tanker, but it's a similar idea in that a second vessel is used.