I agreed that the ISS is NOT built for space exploration. Usually I would say scrap the whole manned mission to Mars and fix the economy first but I will say this.
If you're going to built a multi-purpose vehicle, make the ship BIGGER. You have about (at least) six crew members riding in a giant tin can and if you're using a (FAILED) Orion space capsule, you won't have enough leg room, let alone privacy. Also you can't be weightless for the entire journey or your bones will become brittle. You need a ARTIFICIAL GRAVITY ROTATION DRIVE, similar to the ships from the 2010 and MISSION TO MARS movies. You can't go into deep space in a small (been there, done that) space capsule or otherwise you'll go cuckoo for coco puffs. If you're going to build a ship, think big and do it right. Also it wouldn't hurt to name the ship, ENTERPRISE
:) Peace.