my plan would be to separate the boosters too, you just need them stuck together at launch. or another plan would be to keep them together all the way to mars,

my plan would be to separate the boosters too, you just need them stuck together at launch. or another plan would be to keep them together all the way to mars, and you have a habitation unit above the boosters which is their combined surface area. when you launch the habitation unit you can later land another one next to it the to tile them together.