Faster propulsion is obviously needed and I still wonder if the foam used in the Bigelow inflatable craft can be infused with powdered lead for shielding.
Doesn’t need to be lead... Justa few layers of this...
http://en.wikipedia.org/wiki/Demron
Also the inflatables walls can have two sets of “bladders” in them, one for fresh water and one for recyckled/waste water, and use the water to act a radiation shield/ temprature stabilizer....